Dr. Dawn Barker is a child and adolescent psychiatric expert. She’s also a writer and a friend of mine. We’re both intrigued by the workings of the mind and feel deeply for those who suffer from mental illness and those who love them. Dawn’s new book Fractured weaves a suspenseful tale about a young woman suffering post-natal depression. It’s just been released by Hachette Australia and I can’t wait to read it.
I’ve done some research about the link between cannabis use and schizophrenia, but I’m no expert, so I asked Dawn to write an article detailing the most recent findings. Please use the comments section to ask Dawn any questions you may have. I will be!
Drug Abuse and Psychosis
Dr. Dawn Barker, Child & Adolescent Psychiatrist. MBChB, FRANZCP, Cert C&A Psychiatry
In Thrill Seekers, we meet a group of adolescents who – like many teenagers − use drugs recreationally. One of the main characters, Douggie, then becomes psychotic and develops schizophrenia. Many of us know a friend or family member who’s had a similar illness after drug use and are left wondering: what is the relationship between drug use and psychosis?
What is psychosis?
Psychosis refers to a group of symptoms mainly characterized by hallucinations and delusions. Hallucinations are abnormal sensory perceptions: hearing, seeing, tasting, feeling or smelling something that isn’t actually there. The sufferer might hear voices talking about them, feel insects crawling on their skin, or see faces on the wall. Delusions are abnormal, false beliefs that are held with unshakeable conviction. A deluded person may believe that they are someone special, that they are being followed, or are guilty of something terrible. A psychotic person’s speech can be difficult to follow as their thoughts are disordered, and they lose insight, that is, they are not aware that their beliefs or sensations are abnormal. This can make it very difficult to persuade a patient to seek help and accept treatment.
Most people think of schizophrenia when they think of psychosis, but that’s not necessarily the case: psychotic symptoms can occur briefly and transiently (when using drugs, or when medically unwell), or can occur as part of another psychiatric illness such as depression or bipolar disorder. If the symptoms aren’t secondary to anything and become chronic and disabling, the diagnosis changes to schizophrenia.
Drug use and psychosis
There is no doubt that drugs can cause psychosis. Some drugs – the hallucinogens like LSD and ‘magic mushrooms’ – are used to deliberately alter sensory perceptions. However, psychosis is often an unwanted reaction. As a psychiatrist, I’ve seen hundreds of patients brought into emergency departments − often by the police − with distressing, acute psychosis after abusing drugs such as amphetamines, cocaine or cannabis. Thankfully, most of these patients recover when the drug is out of their system after a few hours or days – we call this a substance-induced psychosis.
What is more worrying is the patient whose psychosis persists even after the acute effects of the drug have worn off. Some of these patients are eventually diagnosed with schizophrenia. Are drugs responsible for this?
The relationship between illicit drug use – particularly cannabis – and schizophrenia is a controversial one. Many patients with schizophrenia have used drugs, but many have not. And of course, the majority of people who use cannabis don’t develop schizophrenia. We know that people with a psychotic illness have a higher rate of cannabis use than the general population, but this could be explained by them being drawn to drug use as a way to cope with their symptoms.
As more long-term studies are analyzed, the links are becoming clearer and the most recent evidence is this:
- If you have a psychotic illness and used cannabis in adolescence, you develop the illness 2-3 years earlier than those who didn’t use cannabis. This is significant, as we know that an earlier age of onset is associated with a poorer outcome. Using cannabis in adolescence makes you up to twice as likely to be diagnosed with schizophrenia in adulthood, and this is a dose effect: the more you use, the more likely the diagnosis is.
- Using the drug at a younger age is most risky: cannabis use at the age of 15, but not age 18, is associated with the higher rates of schizophrenia. It’s possible that one of the chemicals released in the brain when using cannabis, dopamine, is the culprit. We use drugs that block dopamine to treat schizophrenia.
- Cannabis use comes before psychotic symptoms appear, rather than the illness leading to more drug use.
Some people have a gene that, if present, appears to interact with adolescent cannabis use to cause psychosis. Thankfully, schizophrenia is rare, occurring in approximately 1% of the population. Cannabis use in adolescence is just one of several factors that interact to cause the illness, but it’s a significant factor that, if taken out of the equation, could reduce the rates of schizophrenia by 8%.
It’s unrealistic to expect young people to stop using cannabis completely. But we need to understand that its use in the teenage years does increase the risk of developing schizophrenia and we have no way of knowing which young person will be affected. As anyone who has suffered from – or watched someone go through − this illness will agree with, preventing even one case would make a huge difference to many lives.
For more information or if you, or a love one, need help, please contact:
1. Your local doctor or emergency department
- 2. Lifeline: 131114
- 3. Kids Helpline: www.kidshelpline.com.au 1800 551800
- 4. Headspace: www.headspace.org.au
Large M et al. Cannabis use and earlier onset of psychosis: a systematic meta-analysis. (2011). Arch Gen Psychiatry 68(6):555-61.
Arseneault et al. Causal association between cannabis and psychosis:
examination of the evidence. (2004). British Journal of Psychiatry 184:110-117