In Australia, which has had the highest opioid mortality per capita in the OECD, studies found that "overdose fatality is not a simple function of heroin dose or purity. There is no evidence of toxicity from contaminants of street heroin in Australia." Drug Free Australia claims that other causes of death such as suicide, murder and accidents are an effect of the drug themselves, not of their purity or otherwise. Addiction Drug Free Australia argues "Regarding the freedom of choice of those addicted to a drug, it is important to recognize that addiction is defined as compulsive by its very nature and that addictions curb individual freedom." ... "As is the case with alcohol addiction, illicit drug addictions likewise serve to keep many such users functionally in poverty and often as a continued burden on friends, family and society. Where it is argued that all disabilities are a burden on society it must be recognized that most disabilities are not the result of a choice, whereas the decision to recreationally use illicit drugs is most commonly free, and with the knowledge that they may lead to an abundance of addictions." Health arguments for drug law reform There is evidence that many illicit drugs pose comparatively fewer health dangers than certain legal drugs. The health risks of MDMA (Ecstasy) have been exaggerated for instance, the risks from cannabis use also overstated, and health problems from the use of legal substances, particularly alcohol and tobacco, are greater, even than from cocaine use for example (occasional cocaine use does not typically lead to severe or even minor physical or social problems). Health benefits Many trials have shown beneficial effects associated with psychoactive drug use: There is evidence that MDMA (ecstasy) can treat or cure post-traumatic stress disorder and anxiety in cases of terminal illness. LSD has been widely researched as a therapeutic agent, and has shown effectiveness against alcoholism, frigidity and various other disorders. See Psychedelic therapy. Researchers at Harvard-affiliated McLean Hospital found members of a religious group regularly using peyote scored significantly better on several measures of overall mental health than did subjects who did not use the hallucinogen. A 2007 study, by Santos et al. found that users of ayahuasca scored better on tests measuring anxiety and hopelessness than people who did not use the drug. Quality control According to a World Health Organisation report: "As cannabis is an illegal drug