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Evidence regarding the effects of recreational cannabis legalization on public health is inconsistent. Future research should assess heterogeneous policy design, differential effects on population subgroups, and effects related to characteristics of legal cannabis supply.

States are adopting policies that expand cannabis access to larger proportions of the US population than ever before, as described in an accompanying Health Affairs Health Policy Brief. Past-year cannabis use increased from 10.4 percent of US adults in 2002 to 15.3 percent in 2017, and the proportion of past-year users reporting near daily use doubled between 2006 and 2016. During that same period, perceived great risk from smoking cannabis declined among those ages twelve and older, going from 38.3 percent in 2002 to 26.1 percent in 2017. It is important to consider whether perceptions about risk are accurate and what may be the larger population health benefits and harms associated with expanded cannabis access.

In this brief, we summarize research on how cannabis legalization relates to use of the substance and key population health outcomes. We focus on recreational laws because of their broad application and ability to affect public health, although we include some studies on medical cannabis laws with generalizable or relevant findings. A detailed summary of representative studies in these domains is provided in supplemental appendix tables 1–7. We conclude by outlining areas ripe for future research and policy consideration related to safely legalizing cannabis.

Cannabis Use And Health

Research suggests that cannabis use is associated with both positive and negative health effects. The term cannabis refers to parts of or products derived from the plant Cannabis sativa that contain substantial amounts of tetrahydrocannabinol (THC)—the substance primarily responsible for cannabis’s high-inducing effect. Although it is claimed that cannabis and its derivative substances improve outcomes for many disorders, there is only strong scientific evidence suggesting that it is an effective treatment of three conditions: in treating chronic neuropathic pain in adults, as an antiemetic after chemotherapy treatment, and for improving patient-reported multiple sclerosis symptoms.

Demonstrated adverse effects of short-term cannabis use include impaired short-term memory, altered judgement that increases engagement in risky behaviors, and impaired driving. Heavy and long-term cannabis use in adolescents carries substantial risks, including altered brain development and cannabis dependence, which is correlated with elevated risk of using other illegal drugs. Emerging literature suggests that higher-potency cannabis—with a greater THC concentration—may intensify cognitive impairment, severity of dependence, and adverse psychological outcomes. Although cannabis use has been associated with poor educational outcomes and mental illness, it is challenging to attribute causality to these complex, multifactorial outcomes.

The mechanism of consumption likely affects cannabis’ health effects. Although large population studies have not identified an association between cannabis smoking and lung cancer, the link cannot yet be ruled out, as cannabis smoke contains carcinogens.

Effects of Cannabis Legalization

Evidence is emerging on the public health impacts of cannabis legalization. Here we summarize current research regarding the relationship between recreational and, to a lesser degree, medical cannabis legalization and various outcomes that is key to understanding the public health policy implications. We also highlight three areas ripe for future research: additional measures of cannabis use, use disorder, and product type; heterogenous policy design; and differential effects by population subgroups.

CANNABIS USE

Cannabis use is best operationalized through measures of both prevalence (past-month or past-year use) and intensity (for example, number of days used, total grams consumed, potency per dose). Findings on the relationship between recreational legalization and cannabis use among adults are inconclusive, and effects may differ by age group. Using a large, nationally representative survey across several years, two studies observed increased prevalence of past-month cannabis use and frequent use for adults ages twenty-six and older in states with recreational legalization but did not report similar changes among young adults ages 18–25. Other research has identified increases in cannabis use prevalence and intensity among college students who fall within the 18–25 age range. Evidence on the impact of legalization on youth cannabis use remains inconclusive, with research identifying increases, decreases, and no change in use prevalence and intensity measures.

As Rosanna Smart and Rosalie Pacula note, medical cannabis laws, which apply to more limited sectors of the population than do recreational laws, have not been associated with increases in the prevalence of youth (ages younger than eighteen) cannabis use. Although these laws appear to correlate with increased use among adults, subgroup analyses suggest that the evidence remains mixed for young adults ages 18–25. Some studies find that medical legalization has no effect on past-month use or use intensity for young adults, although Christine Mauro and colleagues observed increases in use intensity for males in this age range.

Notably, product characteristics of the legal supply affect the relationship between legalization and cannabis use and use intensity. Early research describes the evolution of product type, potency, and price after legalization in Washington State. Similar research is needed on the legal medical and recreational markets in other jurisdictions to capture how cannabis market characteristics affect consumption patterns.

CANNABIS USE DISORDER

Research on the effects of cannabis legalization on cannabis use disorder is relatively nascent, offering inconclusive findings and suggesting that effects may differ by age group. As Smart and Pacula summarize, medical legalization increases, decreases, or has no effect on self-reported prevalence of or treatment admissions for cannabis use disorder. The few studies that consider heterogenous policy effects of medical cannabis laws suggest that the presence of commercial dispensaries increases both overall and youth cannabis use disorder treatment admissions.

This literature is inconclusive partly because the common outcomes used to measure cannabis use disorder—self-reported symptoms or treatment admissions—are likely influenced by legalization without actually changing prevalence of cannabis use disorder. For instance, by changing social norms around problematic cannabis use, legalization may reduce the likelihood that an individual will self-report symptoms of cannabis use disorder. Similarly, given that treatment admissions for cannabis use disorder often occur through the criminal justice system, legalization may affect written and de facto policies governing law enforcement treatment referrals for cannabis use disorder with or without affecting cannabis use disorder prevalence.

CANNABIS-RELATED HOSPITALIZATIONS AND POISONINGS

Cannabis legalization may result in increases in hospitalization and emergency department visits related to cannabis abuse and dependence and injuries occurring under the influence of the substance. A 2020 narrative review reported that cannabis-related hospitalizations in Colorado increased after recreational legalization, above and beyond earlier additions associated with medical legalization. A rigorously designed study found that the presence of recreational cannabis dispensaries, but not enactment of a recreational cannabis law, is statistically positively associated with poisonings involving cannabis dry plant products overall and in those younger than twenty-one. However, because of data limitations, this study fails to consider exposures to other cannabis product forms that are of particular concern for youth, such as edibles.

DRIVING SAFETY

Potential increases in car accidents involving cannabis use are a chief concern among those disfavoring legalization. Simulation studies suggest that cannabis intoxication impairs driver reaction time, spatial perceptions, and decision making. Detection of cannabis in drivers has tripled from 4.2 percent of fatally injured drivers in 1999 to 12.2 percent in 2010, although it remains unclear how much of this increase can be attributed to cannabis policy liberalization.

Research investigating the relationship between cannabis legalization and driving safety typically leverages fatal crash data. However, less than 0.5 percent of crashes are fatal, so research using data sets that fail to capture nonfatal injuries underreport traffic accidents associated with driving under the influence of cannabis.

Even among studies that use fatality data and consider policy heterogeneity, findings vary from significant positive to significant negative to insignificant relationships between medical cannabis laws and traffic fatalities. Research on recreational cannabis laws is similarly mixed, likely as a result of methodological differences and confounding variables.

USE OF OTHER SUBSTANCES

The extent to which cannabis interacts with other substances heavily influences the public health implications of legalization. In particular, whether cannabis is a complement or substitute to alcohol, tobacco, or opioids is a critical consideration for legalization policy. The effect of legalization on substance use likely differs by substance and user age.

Overall, the literature on the effects of cannabis laws on alcohol use remains mixed for both adolescents and adults, suggesting both substitution and complementary relationships. Studies of recreational cannabis laws have identified both significant declines and insignificant effects on alcohol use with cannabis and without cannabis, as well as intensity of alcohol use. The emerging literature on tobacco is similarly inconclusive but has begun to assess differential effects of legalization across tobacco products. For example, Rebekah Coley and colleagues find that recreational legalization increases e-cigarette use among adolescents but has no effect on cigarette use. Early evidence on medical cannabis laws suggests that the complementary or substitutive nature of the relationship between alcohol or tobacco and cannabis depends on policy restrictiveness and the age of the consuming population.

Research has also focused on the potential for cannabis legalization to address opioid-related harms. A growing minority of states recognize opioid dependence as a qualifying condition for medical cannabis access. Although older studies identified a negative association between medical cannabis laws and opioid mortality, subsequent replications using additional data years have suggested that omitted variable bias may have driven earlier findings. More recent research highlights the importance of considering policy dimensions in evaluations of legalization policies. For example, the existence of dispensaries in medical or recreational legal markets, not legalization alone, may contribute to any observed effect on opioid mortality. Although researchers find (with important exceptions) that opioid prescribing is negatively associated with medical legalization or certain features of medical cannabis markets, this literature may inadequately control for changes in public and private policies and programs targeting opioid misuse.

For more detailed information about legalization and noncannabis substance use, we refer readers to reviews from Gabrielle Campbell and colleagues, Smart and Pacula, and Meenakshi Subbaraman.

Future Research Directions

Although more research is needed regarding the public health consequences of a legal cannabis supply for adults, we have elucidated what is known about four key health outcomes: cannabis use and use disorder, cannabis-related hospitalizations and poisonings, driving safety, and other substance use. Expansion of cannabis research into understudied areas may help address some of the existing inconsistent evidence.

For instance, future research should evaluate specific provisions that govern the legal market. Features of medical and recreational cannabis laws, such as whether a jurisdiction allows dispensaries, likely affect health outcomes and explain discrepancies between studies that do not stratify states by relevant provisions. Although some studies assess the effect of recreational dispensaries on cannabis use, unintentional cannabis exposure, motor vehicle fatalities, and opioid mortality, differentiating states by provisions is not as common in recreational legalization research compared with the more established literature on medical cannabis laws. Further, many studies only evaluate provisions related to legal supply methods (for example, dispensaries, home cultivation), ignoring other elements of the regulatory framework that may have significant implications for public health outcomes. These include provisions such as taxation and advertising restrictions. Evaluations of provisions that govern legal markets could benefit from a categorization system that differentiates states on the basis of multiple characteristics. In addition, analyses should distinguish between policy implementation and effective dates.

Researchers should also consider the public health effects of different characteristics of the legal cannabis supply, including product type, price, potency, and sourcing. Cannabis legalization, particularly commercialization, has the potential to transform the cannabis market. For instance, there has been a proliferation of high-potency products in legal cannabis markets, both in the US and abroad. Novel extracts also make up a rapidly growing market segment. Given public perceptions that alternatives to smoked cannabis products are healthier and more efficient to consume, it is critical to assess their public health effects. Use will also be shaped by the post-tax retail price, and as anticipated, cannabis prices have fallen steeply in states that have legalized recreational use. Thus, researchers should prioritize evaluating the effects of different taxation approaches (for example, ad valorem or based on THC content) on use.

Further, the 2020 vaping crisis associated with diluted THC-containing products raises concerns around unregulated cannabis markets in both legalized and nonlegalized states, heightening the need to study the public health effects of legally versus illegally produced cannabis products. Notably, cannabis markets vary at the local level, and the cannabis industry will continue to evolve in response to federal and state policy changes. Thus, establishing data systems capable of capturing local characteristics of cannabis markets over time will be essential.

It is also critical that researchers expand the study of heterogeneous policy effects across population groups. Our review highlights several studies that evaluate differential effects by age. Researchers should also build on the notable research studying effects by race and ethnicity to investigate why legalization may exert differential effects on cannabis and other substance use for different populations. Cannabis legalization is promoted as a tool to advance social equity, yet legalization has the potential to create or exacerbate socioeconomic and health inequities. Having a criminal record has implications both for health and for economic well-being. Although declines in adult arrests follow cannabis legalization, racial disparities in arrest rates persist, and more research is needed on how the financial and remaining criminal penalties for cannabis violations are distributed across demographic groups. Whether health and other harms associated with cannabis-related criminal justice contact continue to be concentrated among racial and ethnic minorities after legalization deserves careful study.

Beyond criminal justice contact, the design of cannabis markets has health equity implications. Low-income and racial/ethnic minority communities, as well as youth, are especially vulnerable to the commercialization of cannabis. For instance there is some evidence that cannabis dispensaries are concentrating in minority communities. Researchers should prioritize an examination of the differential impact of attributes of legalized markets—including taxation mechanisms, location of cannabis outlets, marketing strategies, product design, and potency—
by social class, race, ethnicity, and age. Further, recent controversies over the effectiveness of social equity provisions embedded within cannabis policy reform call for researchers to evaluate whether these initiatives are achieving their intended effects or producing new inequities.

Even if researchers fill these gaps in the literature, data and methodological challenges limit our ability to draw conclusions about other impacts of legalization. For instance, research could be strengthened by adoption of a clear, consistent, and expansive definition of cannabis “use” across data sources. As Beau Kilmer and Rosalie Pacula highlight, research must move beyond measures of prevalence to include measures of use intensity, such as days used, total grams consumed, and potency per dose. Although researchers should work to develop standardized definitions for and methods to collect dosage information that is comparable across products, it is important to acknowledge that these measurement improvements may add significant costs to study designs and must be weighed against feasibility.

Another important area for methodological and data improvements is in understanding how cannabis legalization relates to driving safety. There exist challenges to reliably measuring THC impairment in drivers (for example, in blood), and uncertainty remains over what level of THC in the blood leads to impairment. In addition, future research should clarify how alcohol and cannabis co-use affects driving impairment. Improved data sources that include information on crashes and fatalities by substance type are essential to fully assessing the impact of legalization on driving safety.

Policy Implications

As policy makers design or revise legal markets, it is important to note that research on early recreational legalization adopters may not be generalizable to all states and localities. The states subject to the most research so far (Colorado, Oregon, and Washington) all had expansive medical programs established before recreational legalization and mostly adopted commercial approaches toward the recreational market. It is unclear whether states with less commercialized medical programs or that adopt different supply chain architectures for recreational supply will experience similar effects on use and public health outcomes.

Nevertheless, there are opportunities for policy makers to incorporate a public health perspective in the design of legal cannabis markets. These include suggestions based on lessons learned from tobacco and alcohol policy and recommendations that focus on youth cannabis use. Other important policy goals may include minimizing drugged driving, unwanted contaminants, and co-substance use. Policy makers may also consider adopting alternative legalization models beyond commercial markets and should thoughtfully incorporate social equity considerations into legalization design and oversight through provisions that address socioeconomic and health disparities. Finally, policy makers should work with researchers to evaluate the impacts of their own legalization schemes as they unfold.

(Editor's Note: This article was conceived and drafted when Haffajee was employed at the RAND Corporation, and the findings and views in this article do not necessarily reflect the official views or policy of her current employer, the US Department of Health and Human Services, nor the US government.)

What marijuana research in humans tells us so far about the drug’s benefits and drawbacks.

It’s mid-October, and Staci Gruber is preparing to testify before Congress. It’s not the first time she’s brought her expertise before policymakers; she’s studied marijuana in brains young and old for the better part of three decades.

Besides being on the psychiatry faculty at Harvard University, Gruber is the director of Marijuana Investigations for Neuroscientific Discovery (MIND) and the director of the Cognitive and Clinical Neuroimaging Core at McLean Hospital outside of Boston. Her research focuses on clinical studies in marijuana users, often employing functional MRI (fMRI) technology to see exactly what parts of the brain the drug affects.

“The important part is to try to leave the emotional rhetoric aside,” she says, ahead of her testimony before lawmakers. “What matters is what the data and the science tell us.”

And the research landscape, so far, is about as complicated as the drug itself. Some studies show that marijuana may provide relief for patients with a slew of conditions, such as anxiety, chronic pain and even cancer. Yet others find that the drug can slow cognitive function and may worsen some mental health conditions.

We also still don’t have a clear picture of how marijuana works in different people, Gruber says. Just five years ago, when she started MIND, Gruber spotted a research gap — virtually no clinical studies were conducted on the effects of medical marijuana on the brain. “I could find nothing in the literature,” she says. 

Data on how marijuana works in people over time are sparse. U.S. research on cannabis remains bottlenecked because of limitations on studying the Cannabis sativa plant, some parts of which remain a Schedule I drug. Even though medical marijuana containing the psychoactive compound THC is legal now in 33 states and the District of Columbia, the Drug Enforcement Administration still defines it as a substance with “no currently accepted medical use” and a “high potential for abuse.” Policymakers, eager to better understand how to regulate the drug, occasionally hold sessions with scientists, including Gruber. But with scarce clinical results, she and her American peers find it hard to draw broad conclusions. In countries like Israel and Canada, where barriers to studying cannabis are lower, piecing together the puzzle of who marijuana affects, and how, is only slightly easier.

Complicated Cognition

How does weed affect cognition? That might depend on how and when people use it. Some teenagers who use marijuana recreationally appear to have slower brain function and lower IQs. On the other hand, people with medical conditions who stay slightly baked to manage their symptoms may actually see an increase in brain function. 

In a 2011 report on recreational users, Gruber and her team recruited 34 chronic marijuana smokers and divided them into two groups according to when they started using. They were then given a number of cognitive tests. The team found that those in the study who started using marijuana before age 16 had the worst test performances — and smoked twice as often as other users.

But a 2018 clinical study on medical marijuana users showed very different effects on the brain. The study looked at patients with a variety of conditions, including pain, anxiety, sleep disorders and gastrointestinal problems, before and after taking marijuana via their preferred method of use — smoking, eating or topically applying. Three months after patients started treatment, varying from one or two doses a week to multiple doses per day, the researchers observed that their brains had more activity in the prefrontal cortex, the area associated with cognition, decision-making and executive function. They also saw an increase in task performance among the users, signifying a boost in cognitive function. 

In addition, the treatment quelled their symptoms — most medical marijuana users in the study saw an increase in quality of life and alleviation of their ailments. The results weren’t a huge shock for Gruber. 

“Recreational consumers and medical users just aren’t the same,” she says. “The goal of use is totally different.”

That could explain why some recreational users seek out super-loaded quantities of tetrahydrocannabinol (THC) in the strains they smoke. THC is what makes users high; its sister component, cannabidiol (CBD), does not. From 1995 to 2014, THC content in recreational marijuana increased from 4 to 12 percent, while the CBD content in modern-day weed is barely 0.15 percent.

CBD, on the other hand, is growing in popularity as a medicinal treatment for inflammation, pain and anxiety. But the jury’s still out on how well the compound works as a remedy. In 2018, Gruber’s team began the first clinical trial on CBD in patients with anxiety, with results expected as early as this year.

Mind Under Matter

Our understanding of marijuana’s effect on mental health is murky. Some studies suggest it might exacerbate conditions like schizophrenia or psychosis, but the results aren’t always black and white.   

In a 2017 clinical trial of 88 patients with schizophrenia, researchers in the U.K. administered 1,000 milligrams of CBD each day to about half of the study participants. They took the supplement along with their typical regimen of antipsychotic medications. At the end of six weeks of treatment, the people who received CBD reported greater alleviation of symptoms than those who only stuck to their normal medications. 

But another study from just this year found that weed might actually correlate with an onset of psychosis. Researchers in the U.K. surveyed more than 900 patients who had been diagnosed with their first psychotic episode, and over 1,200 participants who had not been diagnosed with psychosis. They asked about lifetime cannabis use and found that daily marijuana users had the highest risk of developing the condition.

That risk may be linked to the concentration of THC in a particular cannabis product, however. In the same study, researchers split weed users into two groups: those who typically smoked marijuana with a THC concentration of less than 10 percent, and those who used high-potency pot with a concentration of 10 percent or higher. They found that high-potency users had a fivefold increased chance of developing psychosis. Taken together, these findings help show that our brains have very different reactions to CBD and THC — which might be why medicinal users often experience such different results from recreational users.

Grandpa’s Weed

Marijuana use is skyrocketing among the elderly — reports have suggested it has increased as much as tenfold among seniors over the past decade. And the drug might be an effective measure to treating chronic pain and chemotherapy side effects like nausea, which could explain the climbing usage rates.  

A small clinical study published in the German journal Der Schmerz indicated that an oral medication form of synthetic marijuana, known as dronabinol, helped relieve pain in patients older than 80. According to the results, released in October, more than half of patients experienced some level of pain relief after a year of taking the medication. 

And a much larger study found positive results among a slightly younger crowd. In Israel, a team of researchers administered a questionnaire about quality of life before and after patients at a specific clinic started using cannabis. The results compiled data from over 2,700 patients older than 65, most of whom had chronic pain or cancer symptoms. More than 90 percent of patients noted an improvement in their condition after six months of using the drug.

In another study, the same researchers also analyzed data from cancer patients who routinely used medical marijuana to manage their symptoms. Drawing results from just over 1,200 patients, they found that over 95 percent reported an improvement in their symptoms, which ranged from sleep problems and lack of appetite to weakness, nausea and pain. 

The German and Israeli studies concluded that the drug was safe and effective in older populations seeking relief from pain or cancer-related symptoms. Marijuana might be a positive alternative for older folks looking for relief — although not every medical condition responds as drastically to treatment as others.

A Mixed Bag for MS

While a handful of studies have found marijuana to be a potential treatment for the pain and spasticity that come with multiple sclerosis (MS), not all clinical research shows a benefit.

The largest randomized clinical study on MS and marijuana to date, according to the National Multiple Sclerosis Society, found that different oral THC medications helped patients manage symptoms like spasticity and sleep struggles, while there was no improvement in tremor or bladder symptoms. And another clinical study done in the U.K. in 2013 showed that oral THC, while not unsafe, didn’t slow the progression of the disease. 

But a 2012 study did find that short-term marijuana use may help with those physical symptoms. Researchers at the Center for Medicinal Cannabis Research at the University of California, San Diego, studied the effects of inhaled cannabis on pain levels and spasticity control. Thirty participants smoked marijuana once a day for three days, and noted that their spasticity and pain levels decreased more than for those who took a placebo. 

Preliminary results from a 2019 study show the picture is different when it comes to the mental effects of marijuana on MS patients. Researchers in Canada followed study participants, who had been smoking at least four times a week for many years, as they abstained from marijuana for 28 days. The research team took fMRI scans as they were weaned off the drug, and noted that they showed an increase in cognitive function. Certain areas of the brain that were normally inactive in the participants started to reawaken, and their performances improved in cognition tests.

Smoke in the Wind

The bottom line is this: Research on marijuana remains inconclusive. Results differ from person to person, depending on why and how they use the drug.

To date, only a few medications — dronabinol, nabilone and cannabidiol — have received FDA approval. But they’re intended for use by a select group of patients: those with rare forms of epilepsy, those who have side effects from chemotherapy or those with severe weight loss caused by AIDS. Dronabinol and nabilone, which are both oral synthetic forms of cannabis, are defined as Schedule II and III drugs. That means the DEA sees a moderate to high potential for dependence or abuse, although certain patients are still allowed to use the drug for its medicinal benefits. In 2018, a CBD-derived oral medication called Epidiolex was approved as a Schedule V, meaning it is regulated as a drug with the least potential for abuse. 

But with recreational marijuana use on the rise, researchers like Gruber are pushing for more concrete evidence on the drug’s effects. She’s certain that it’s far from vanishing from the public eye. 

The many benefits of steroids have created a culture of abuse in sports like weightlifting, bodybuilding and cycling. Yet you can improve your health without using these dangerous drugs. Learn healthy ways to quickly recover, build muscle and get stronger to safely enhance your performance in any sport.

Doing resistance exercises like weightlifting can give you many of the positive effects of steroids without the long term risks. And exercise can increase the natural steroid content of your muscles, according to a January 2015 review in the Journal of Steroid Biochemistry and Molecular Biology.

Types of Steroids

Your body makes natural steroids from the sterols present in the food you eat each day. Scientists can also make synthetic steroids in a laboratory.

Athletes most often abuse anabolic (testosterone-based) steroids, but corticosteroid (cortisol-based) drugs like prednisone have become increasingly common in sports too. This dramatic increase has brought corticosteroids under greater scrutiny. An athlete should thus avoid these steroids as well, unless there's an imperative medical reason to use them, advises an October 2012 report in the Scandinavian Journal of Medicine and Science in Sports.

There are also two distinct categories of anabolic steroids, according to a February 2019 fact sheet from StatPearls. The 17 alpha alkyl derivatives like oxandrolone make up one group. The 17 beta ester derivatives like nandrolone phenpropionate make up the other. The latter drug was one of the first steroid substances used for its benefits, and the International Olympic Committee banned it in 1974. It's important to note that the U.S. Drug Enforcement Agency deems all anabolic steroids are controlled substances, with a harsh penalty for manufacture, possession or use.

Build Muscle Mass

The many side effects of anabolic steroids make it unethical to give them to healthy adults. However, scientists can test their impact by studying the archival data of admitted users. The authors of a September 2014 report in PLoS One used this method to measure the benefits of steroids on muscle mass. The researchers compared the data of 10 steroid users to seven control subjects. Results indicated several positive effects of steroids, including greater muscle mass and larger fiber area. The authors believe that these changes would likely enhance the performance of the users.

Yet you can get similar results without taking anabolic steroids. The September 2014 report in PLoS One tested middle-aged, male subjects who were active and fit. A February 2013 paper in the Annals of Endocrinology showed similar results in similar subjects. These researchers found that eight weeks of moderate weight training resulted in increases in muscle strength and size in eight healthy, middle-aged men. That training also increased the subjects' circulating levels of the natural steroid testosterone.

Increase Exercise Capacity

Anabolic steroids have several legitimate medical uses, and some of those uses would offer a competitive advantage to an athlete. For example, the authors of an April 2014 report in Nutrition in Clinical Practice tested 32 people with chronic obstructive pulmonary disease, or COPD. Such patients are often not in good shape fitness-wise because of their decreased lung capacity. Compared to baseline, six weeks of anabolic steroid use increased the exercise capacity and life quality of these patients.

However, you can get nearly identical results with water-based training. A June 2013 article in the European Respiratory Journal discussed the evaluation of 53 COPD patients. These researchers had the subjects do water-based aerobics and weightlifting for eight weeks. This treatment increased exercise capacity and life quality, compared both to the baseline and a control group. Interestingly, water-based training also outperformed land-based training. Water-based exercise also tends to cause less injury because the water's buoyancy both increases resistance and offers more limb support.