Environment Predicts Schizophrenia Risk Better than Genes

Rob Wipond

We should focus more on reducing or preventing specific environmental and lifestyle risk factors for schizophrenia, because genetic risk factors have no predictive capability whatsoever, according to a study in The Lancet Psychiatry.

The team of German researchers studied 750 male patients diagnosed with schizophrenia for whom they had genetic information as well as extensive background and clinical information about factors such as marijuana use, brain injuries, and traumatic experiences. They drew on the latest studies of genes and schizophrenia, and then evaluated which information was more useful for predictive purposes. “Specifically, we investigated the potential effect of schizophrenia risk alleles as identified in the most recent large genome-wide association study versus the effects of environmental hazards (ie, perinatal brain insults, cannabis use, neurotrauma, psychotrauma, urbanicity, and migration), alone and upon accumulation, on age at disease onset, age at prodrome, symptom expression, and socioeconomic parameters,” they wrote.

They found that environmental factors became a significant predictor of schizophrenia as the number, frequency and intensity of those factors increased. In contrast, they found that genetic risk factors “did not have any detectable effects.”

“These findings should be translated to preventive measures to reduce environmental risk factors, since age at onset of schizophrenia is a crucial determinant of an affected individual’s fate and the total socioeconomic cost of the illness,” the researchers concluded.

(Abstract) Accumulated environmental risk determining age at schizophrenia onset: a deep phenotyping-based study (Stepniak, Beata et al. The Lancet Psychiatry. November 2014. doi: 10.1016/S2215-0366(14)70379-7)


  1. The study concluded that
    ” In particular, cannabis use—an avoidable environmental risk factor—is highly significantly associated with earlier age at prodrome (p=3·8×10−20). By contrast, polygenic genome-wide association study risk scores did not have any detectable effects on schizophrenia phenotypes.”

    Many states are adopting laws permitting easier public access to cannabis. It remains to be seen if that easier access results in increased rates of “mental illness”. No doubt the statistical battle that ensues will be similar to one over increased access to concealed-carry pistol permits and liberal gun laws. One side will say that society has benefited and the other that the public has been endangered. One big difference, if someone has been shot, there is no doubt about the diagnosis, or the existence of the bullet that caused the wound.

    Some critical thinkers speculate that gun laws have been relaxed only so that in the long term all guns can be strictly controlled because of some real or perceived increase in gun violence.

    • Tobacco smoke causes lung cancer and no one is banning it. Alcohol consumption can lead to violence and a swath of other problems, social and individual. Given that certain regulations and public health campaigns are introduced the risks may be minimised while a complete ban leads to the “war on drugs” situation we all know.
      Legalise it, regulate it (including the permissible amount of THC, smoking restrictions on driving, age, workplaces etc.), educate about it and allow the social and health workers to deal with the rest.

  2. I’ve been saying this for a long time. Even if there was clear evidence of some kind of correlation with genetics as a predictive factor, which there to date is not, and I doubt there will be, the impact of environment is obvious and so much larger than any genetic effect might turn out to be. The same is observed for things like heart disease and cancer, which have identified physiological markers – the association with genetics is tiny compared with the contribution of stress, lifestyle, and early-life trauma. Since we know for absolute certain that environment accounts for most of the variation in physiological disease states, how much more certain is it that environment is by far the more important variable in a “mental health” condition? Not to mention the fact that genes can’t be changed anyway, while environment can be. Corruption, fear, and egotistical hubris are the only explanations why people continue to seek these genetic explanations when it is clear they will never begin to explain the phenomena that have come to be known as “mental illness.”

    —- Steve