As marijuana use becomes legal in some states, the dominant public opinion is that marijuana is a harmless source of mood alteration. Although the harms associated with marijuana use have not been well studied, enough information is available to cause concern.

/pdf/adverse-health-effects-of-marijuana-use-4ih1jc0uzi.pdf

Adverse Health Effects of Marijuana Use

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(07)61162-3.pdf

Cannabis use and risk of psychotic or affective mental health outcomes: a systematic review

Psychotic syndromes can be understood as disorders of adaptation to social context. Although heritability is often emphasized, onset is associated with environmental factors such as early life adversity, growing up in an urban environment, minority group position and cannabis use, suggesting that exposure may have an impact on the developing 'social' brain during sensitive periods. Therefore heritability, as an index of genetic influence, may be of limited explanatory power unless viewed in the context of interaction with social effects. Longitudinal research is needed to uncover gene-environment interplay that determines how expression of vulnerability in the general population may give rise to more severe psychopathology.

https://sites.oxy.edu/clint/physio/article/theenvironmentandschizophrenia.pdf

The environment and schizophrenia

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(11)61138-0.pdf

Extent of illicit drug use and dependence, and their contribution to the global burden of disease.

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(09)61037-0.pdf

Adverse health effects of non-medical cannabis use

http://www.ukcia.org/research/PsychologicalAndSocialSequelae.pdf

Psychological and social sequelae of cannabis and other illicit drug use by young people: a systematic review of longitudinal, general population studies

The aim of this study was to carry out a comprehensive and systematic review of the literature on drug-use prevention with vulnerable young people. A search of electronic databases was conducted to find evaluations of prevention programmes targeted at high-risk young people and including illegal drug use as an outcome measure. Sixteen relevant studies were found that used a suitable quality of research design, involving at least a comparison group. The most common setting for these evaluations was in schools, where life-skills training interventions showed positive results in reducing drug use (at least in the short term). In the community an intensive multi-component intervention (the Children at Risk program) was the most effective. Across different settings the 11–13 age range appeared to be a crucial period for intervention with vulnerable young people. All of the sixteen studies included in the review were from North America and therefore there is a need for outcome evaluations of targeted drug preve...

The psychosocial consequences of drug misuse: A systematic review of longitudinal studies

Recreational use of illicit drugs (i.e. use not associated with a diagnosed drug problem) may cause psychological and social harm. A recent systematic review found that evidence for this was equivocal. Extensive evidence was only available in relation to cannabis use. This was relatively consistently associated with lower educational attainment and greater use of other drugs. However whether this association was causal was not clear. Cannabis use was less consistently associated with mental illness and antisocial behaviour. Causal relations between cannabis use and psychosocial harm could plausibly be mediated through either neurophysiological effects of cannabis or through social mechanisms related to use of an illegal substance. These different mechanisms might have different implications for harm-reduction policy. Alternatively associations may arise through non-causal pathways such as reverse causation, bias and confounding. In this latter situation, even effective reduction of cannabis use would be u...

How strong is the evidence that illicit drug use by young people is an important cause of psychological or social harm? methodological and policy implications of a systematic review of longitudinal, general population studies

Thomas Oppenkowski

Papers

Psychological and social sequelae of cannabis and other illicit drug use by young people: a systematic review of longitudinal, general population studies

The psychosocial consequences of drug misuse: A systematic review of longitudinal studies

How strong is the evidence that illicit drug use by young people is an important cause of psychological or social harm? methodological and policy implications of a systematic review of longitudinal, general population studies