Should we advise patients with serious mental illness to stop using cannabis?

Advising patients with serious mental illness to stop their cannabis intake tends to be unpopular with patients, and also with some psychiatrists. Patients enjoy using cannabis, and can perceive it as being therapeutically beneficial. Thus, their reluctance to stop their cannabis intake is understandable. The argument of psychiatrists and other mental health-care professionals against giving such advice is that since the effect of cannabis on psychosis is nothing or negligible, psychiatry must not portray itself as a ‘killjoy’ profession, because this could lead to fewer mentally ill patients trusting psychiatrists to help them. On the other hand, Macleod (Reference Degenhardt, Tennant, Gilmour, Schofield, Nash, Hall and McKay2007), in his excellent commentary on Degenhardt et al. (Reference Degenhardt, Tennant, Gilmour, Schofield, Nash, Hall and McKay2007), considers that trying to prevent or reduce cannabis use amongst the mentally ill patients is justifiable, even when one considers its apparently small effect on psychosis. He supports this opinion by underlining that cannabis is not only deleterious on psychosis, but it is also a contributing factor to physical health problems. I agree with the reasons he gave but I also believe that this approach is totally justifiable also on the basis of the effect of cannabis on psychosis only. As clinicians, we should provide the best possible holistic treatment to our patients. Since schizophrenia is a ‘dreadful illness that is substantially unexplained and ineffectively treated’ (Macleod, Reference Macleod2007), it poses unique challenges. Thus, any measure that can contribute towards relieving suffering, however negligible is its effect, should be considered seriously. Also, one must not forget that such measures do not influence patients uniformly, and a negligible measure for one patient can be a significant one for another patient. How can we convince more psychiatrists and more mental health-care professionals to advise patients to stop their cannabis intake? An obvious need is to conduct research into the efficacy of different ways of persuading patients with serious mental illness to refrain from using cannabis.