Dear Dr. Levy: Someone was telling me that marijuana can cause a person to become psychotic. Is there any truth to that?
A: You ask a very interesting question and let me share with you what is known about this topic.
Many studies have shown that rates of psychosis and schizophrenia, a type of psychotic disorder, are higher among those with a history of cannabis use. In addition, early use of cannabis appears to increase the risk of psychosis. It also appears that there is a dose-related affect, meaning that heavy cannabis use increases a person's risk of becoming psychotic. This relationship has been seen among individuals who used cannabis during adolescence, as well as those who had previously experienced psychotic symptom, and those who are at high risk for developing schizophrenia based upon family history.
I also read a recent study that demonstrated that highly potent marijuana, along with frequency of use, appears to be a risk factor for developing a psychotic disorder.
So in summary, cannabis, and in particular heavy cannabis use and the use of potent marijuana, appears to be an independent risk factor for psychosis and psychotic symptom. However, it is also clear that many who use cannabis never develop psychosis.
Finally, it is very clear that those with a positive genetic loading for schizophrenia and psychosis have a greater risk.
Dear Dr. Levy: Do you know if there is any evidence that cocaine can cause brain damage?
A: What makes answering this question a little tricky is that when a cocaine addict is assessed, if there are cognitive problems secondary to possible brain damage, it is hard to know if these problems existed before using cocaine. However, some recent research has tried to answer this question using rats.
In this research, prior to using cocaine, rats were given some cognitive tests to assess their ability to learn a task. After all rats learned this, some were given moderate amounts of cocaine over the course of three weeks, others were given significantly larger quantities, and even others received none. After this time, rats were again exposed to the task they had learned earlier.
What the researchers found was that the rats exposed to large quantities of cocaine made significantly more errors than either those who received no cocaine, or those who were exposed to smaller quantities of cocaine. They also found that these deficits lasted up to one month after receiving the cocaine. Now the researchers believe that heavy cocaine use affects attention, cognitive flexibility, and decision-making.
The researchers also examined the rat's brain tissue and found that cocaine use caused changes in a part of the brain called the prefrontal cortex. This likely was related to the cognitive problems observed.
So in answer to your question, it appears that heavy cocaine use can cause cognitive problems that are related to damage in certain parts of the brain.
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Send questions about addictions or related problems to: Take The First Step, c/o The Eagle-Tribune, 100 Turnpike St., North Andover, MA 01845; or send e-mail to michael_levy@cabhealth.org. Questions will be answered in confidence by a clinical team led by Dr. Michael Levy, director of clinical treatment services at CAB Health & Recovery Services in Peabody and author of "Take Control of Your Drinking...and You May Not Need to Quit."
