Most people who smoke pot enjoy it, but a smaller proportion experience psychotic-like symptoms, such as feeling suspicious or paranoid. The question that polarises researchers is whether smoking cannabis is associated with a risk of developing psychotic problems, such as schizophrenia, in the long term.
Of course, cannabis use is common, while schizophrenia is relatively rare, affecting less than one per cent of the population. Even if cannabis use were to double the risk, over 98% of cannabis users would not develop schizophrenia. Researchers have to tread carefully in evaluating the evidence and avoiding scaremongering.
Although several studies suggest that cannabis users have a higher risk of developing schizophrenia, one key point remains hotly contested. Since the 1960s, cannabis potency and rates of use have risen in many Western countries with high-potency strains now dominating the market. If cannabis were a cause of psychosis, we would expect