The analyses confirm that cannabis is associated with depression. However, the link between cannabis and depression does not appear to be a one-way street. On the one hand, the research team was able to prove that young people who used cannabis were more likely to suffer from depressive symptoms one year later. On the other hand, respondents with depression were more likely to turn to cannabis a year later. The connection appears to be reciprocal: cannabis and depression are mutually reinforcing.

If cannabis were to contribute significantly to the occurrence of psychosis, then psychoses would have to be diagnosed more frequently in regions where people smoke a lot of weed and more medication would have to be sold to treat psychoses. A research team from the USA has investigated this assumption. Study leader Holly Elser and her team analyzed the anonymized disease data of over 63 million people aged 16 and over.