Can Drugs Cause Schizophrenia?

There is a strong connection between schizophrenia and addiction. An estimated 80% of people with schizophrenia smoke cigarettes whereas in the general population smoking is down to about 20%. The same kind of rate can be seen when it comes to cannabis.

As a psychiatrist working with substance users, you are likely to see a lot of people who are on antipsychotic drugs and I always ask why? It is very hard to disentangle how much of their psychosis is due to their overuse of legal highs (prescription drugs) or abuse of cannabis or alcohol.

What is Schizophrenia?

Psychosis is a major group of mental health disorders. The other big subsection is neurosis. The big difference is that in neurosis you are still in touch with reality but in psychosis you lose touch with reality in various ways: it may be hallucinations (false perceptions) or delusions (firmly held false beliefs).

Schizophrenia is a major subdivision of psychosis. The classic symptoms are misperceptions, hallucinations and voices. Practically all the schizophrenic patients I can think of will talk about voices; a lot of them are persecutory but I can think of patients who had voices that told them nice things, for example, they are going to get married in August.

There is a Dutch psychiatrist who has highlighted that hearing voices is not as abnormal as we psychiatrists seem to think, and arguably 30% to 40% of the population have heard voices at some point in their lives. It may be due to stress. It may be at night time when we are more alert but more likely to misperceive our environment: outside noises may have a sinister meaning but it might just be the wind in the trees.

A schizophrenic may be directly troubled by the voices. We talk about command hallucinations when the individual feels obliged to act on them and has difficulty resisting them. That may give them difficulty. Very occasionally they are dangerous. More commonly it’s a loss of drive and/or a loss of initiative, that is the main problem for the schizophrenic.

Another important aspect of schizophrenia is thought disorder: the person is just not able to think logically; it is quite obvious they are jumping around and you can’t follow what they are saying. Their speech betrays the thought disorder underlying it.

Schizophrenia and Cannabis

Both cannabis and amphetamines can cause a paranoid reaction or even psychosis. Certainly cannabis can cause a distortion of reality; sometimes this can be in a pleasant way, and that’s why people like cannabis, but sometimes it can be in a very unpleasant, sinister way.

There is a lot of new research from New York and London showing that the younger people are when they start using cannabis, and the more they use in their teenage years, the more likely they are to develop schizophrenia later in life.

This is to quite a significant extent: schizophrenia may be up to 7 times more likely if the individual starts to use cannabis very heavily when they are only 12 or 13 years old. The prevalence of schizophrenia in the general population is about 1 in 100, but if you abuse cannabis at a young age you can increase the chances of getting it by 6 or 7 times. Considering how serious this illness is, it is a very serious risk to take.

Schizophrenia and Modern Medicine

Nowadays, with antipsychotic drugs, we are very good at treating the acute symptoms of schizophrenia – the positive symptoms, the hallucinations and delusions. But we don’t really have anything that is good for what we call the negative symptoms – the lack of drive and initiative. We are good at getting people out of hospital and managing at home but quite a high proportion will need a lot of help at home.

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