The link between cannabis use and psychosis

Use of cannabis may precipitate schizophrenia in people genetically predisposed to it. There is an ongoing debate among researchers about the link between cannabis and schizophrenia.
The link between cannabis use and psychosis

Raghav was a 24-year-old graphic designer who was brought in for a consultation by his friends in August, 2014. They were from different parts of the country and had been sharing an apartment for over a year. They knew each other quite well and were like a family.

Raghav had recently started accusing them of ridiculing him behind his back. He had told them that he did not trust them anymore. Usually an occasional user, he had been smoking cannabis excessively for the past one week “to get into the zone and produce some amazing work.” As all his friends smoked weed occasionally, they could see that things were not right with Raghav. Apart from the new attitude of mistrust towards them, he had practically stopped eating. He hardly slept. He would lose his temper if someone cajoled him to eat or to go out. And no one dared to set him off because he was physically strong and easily provoked into using his fists.

Adi, 23 years old when I first met him in 2004, was a commerce graduate. He had been working in the accounts section of his father’s firm for a year. He was a quiet, gentle and studious boy and his parents had had no trouble raising him at all.

But something had changed recently. For the past few weeks he had been keeping to himself, often smiling into the distance or muttering as though he were talking to an invisible person. In the beginning he would explain that he had remembered a joke, so the family left it at that. Gradually this behavior became more frequent and he no longer bothered to explain. He started missing work, mainly because of sleepless nights. He started smoking more than ten cigarettes (regular cigarettes) a day, while he had rarely smoked before. One day his mother confronted him. She was horrified to know that the change had begun after he had started smoking weed a few months earlier. His supply was cut off and a strict vigil maintained.

However, there was no change for the better in his behavior in the ensuing months. That’s when he was brought in for a consultation.

Cannabis is considered a recreational drug by many. Its use is legal in many countries, and a large number of people smoke weed. Although research has thrown up contradictory results regarding its role in precipitating schizophrenia, most psychiatrists would agree that:

  • Cannabis can trigger schizophrenia in people predisposed to it, i.e. people who have close relatives with schizophrenia.

  • There is no single gene that accounts for the heritability of schizophrenia. Several unexpressed genes do. These are called risk genes and can be activated by cannabis in those predisposed to schizophrenia.

  • Once schizophrenia develops, it is irreversible.

Both Raghav and Adi had a family history of schizophrenia. Raghav’s paternal uncle had been on treatment for many years. Adi’s maternal uncle had a form of schizophrenia characterized by global deterioration in all areas, cognitive, emotional and social. Also, Adi’s sister was diagnosed with schizophrenia by another psychiatrist in 2008. Their family histories made both Raghav and Adi more vulnerable to the effects of cannabis, as brains of people at risk of schizophrenia apparently react differently to cannabis.

Raghav’s psychotic symptoms were controlled by antipsychotic medications, but he refused to give up cannabis. He left the last session assuring me that he would control his use of cannabis.

Adi made good progress with regular medications for the next 6-7 years, even going to work everyday. Nevertheless, it was evident that he was functioning at a level at least 25-30% below his earlier peformance. He had three psychotic breakdowns in the past 5-6 years, each time after he had missed taking medicines for a few days, deteriorating with each episode. He is currently residing in a psychiatric facility, incapable of anything more than the simplest conversation, his intellect considerably dulled by the illness.

Adi never abused cannabis after his initial experimentation. However, the ball had been set rolling: the risk genes had been activated and the chances of deactivating them were no more than those of toast being turned into bread again.

Smoking weed is like any other activity that people take up. Who thinks that a roller coaster may damage them when they first ride one? People just go along with others in their group as it looks like fun. A roller coaster is more likely to cause disc injury if the rider has a weak back; but it might cause disc injury even if one does not, because individual susceptibility to injury is an unpredictable variable. People don’t know whether they have a weak back or not until something happens.

Likewise, use of cannabis may precipitate schizophrenia in people genetically predisposed to it. There is an ongoing debate among researchers about the link between cannabis and schizophrenia. As there is a genetic overlap between the tendency to develop schizophrenia and the tendency to gravitate towards use of cannabis, both could be expressions of the same genes. No firm conclusions have yet been reached.

As things stand, doctors can only caution people with a family history of schizophrenia to avoid experimenting with cannabis, though not having a family history does not guarantee that cannabis will not precipitate psychosis.

In this series Dr Shyamala Vatsa highlights the fact that teenage changes can mask incipient mental health problems. These articles show how early symptoms of mental disorder can be taken for ordinary teenage behavior. As illustrated by the stories of young people who have suffered unnecessarily, it is important for friends and family to recognize when a behavior is outside normal limits, and seek help before things spin out of control.

Dr Shyamala Vatsa is a Bangalore-based psychiatrist who has been practicing for over twenty years. If you have any comments or queries you would like to share, please write to her at

We are a not-for-profit organization that relies on donations to deliver knowledge solutions in mental health. We urge you to donate to White Swan Foundation. Your donation, however small, will enable us to further enhance the richness of our portal and serve many more people. Please click here to support us.

Related Stories

No stories found.
White Swan Foundation