From the Guidelines
THC can significantly worsen symptoms or trigger episodes in people predisposed to mental illness, particularly with high-potency products and regular use, as evidenced by recent studies 1.
Key Considerations
- For individuals with a personal or family history of psychosis, schizophrenia, bipolar disorder, or severe anxiety disorders, THC consumption may accelerate the onset of these conditions or intensify existing symptoms.
- The risk is particularly high with regular use, high-potency cannabis products, and use during adolescence when the brain is still developing, as noted in a recent position paper from the American College of Physicians 1.
- THC affects neurotransmitter systems in the brain, particularly dopamine, which plays a key role in psychosis and mood disorders, and can cause temporary psychotic symptoms even in people without predisposition, including paranoia, hallucinations, and disorganized thinking 1.
Recommendations
- Those with mental health risk factors should avoid THC entirely or discuss its use carefully with healthcare providers if considering medical cannabis, given the potential for adverse psychosocial events, such as major depression and suicidal ideation 1.
- It is crucial to consider the potential long-term effects of cannabis use on mental health, including the risk of neuropsychological and neurodevelopmental decline, elevated risk for psychotic disorders in adulthood, and higher risk for later depression and suicidal ideation or behavior, as highlighted by the Substance Abuse and Mental Health Services Administration 1.
Important Findings
- Recent studies have shown that cannabis use may have a deleterious effect on adolescent brain development and well-being, with some evidence suggesting an association between nondisordered cannabis use and adverse psychosocial events 1.
- The increasing potency of cannabis products, with THC levels reaching up to 70% in some concentrates, may further elevate the risk for health problems, including mental health issues, as noted in a recent study 1.
From the Research
Effects of THC on People Predisposed to Mental Illness
- THC, a component of cannabis, has been found to be the main culprit causing psychosis and schizophrenia in the at-risk population 2
- THC can also exacerbate symptoms and cause an adverse prognosis in already diagnosed patients 2
- The use of Cannabis sativa is associated with increased risk of developing psychotic disorders, including schizophrenia, and earlier age at which psychotic symptoms first manifest 3
- Cannabis exposure during adolescence is most strongly associated with the onset of psychosis amongst those who are particularly vulnerable, such as those who have been exposed to child abuse and those with family histories of schizophrenia 3
Therapeutic Potential of CBD
- CBD, another compound in cannabis, can counter many of the effects of THC and may have therapeutic potential for the treatment of psychosis following cannabis use, as well as schizophrenia 3
- CBD may have anti-inflammatory and neuroprotective properties, and establishing its role in treating psychotic disorders will require further human research 3
- A systematic review found that there is insufficient evidence for an effect of THC or CBD on symptoms, cognition, and neuroimaging measures of brain function in schizophrenia 4
Risks and Limitations
- The relationship between cannabis and schizophrenia needs further investigation, and more case-control studies and clinical trials with a larger population are needed to get conclusive data 2
- There is very low quality evidence that pharmaceutical THC (with or without CBD) leads to a small improvement in symptoms of anxiety among individuals with other medical conditions, but it can worsen negative symptoms of psychosis 5
- Pharmaceutical THC (with or without CBD) did not significantly affect any other primary outcomes for the mental disorders examined but did increase the number of people who had adverse events and withdrawals due to adverse events 5