June 30, 2023 – Few studies have as massive a sample of individuals being studied as Jefson’s n of over 6 million. But what does this study really tell us? From the outset, Jefson only looked at diagnosed cases of CUD. Far more Danes could have been using cannabis regularly without being diagnosed. If they had also been counted, the hazard ratio for bipolar disorder might have been significantly lower. This is assuming that undiagnosed CUD would be more common than undiagnosed bipolar disorder. Undiagnosed depression, of course, might even be more common than undiagnosed CUD. Furthermore, a diagnosis of CUD in a treatment center or clinic may have alerted clinicians to look more closely for associated comorbidities such as depression and bipolar disorder.

On the other hand, this massive study adds additional weight to the possibility of cannabis possessing psychotogenic power in vulnerable individuals. At the least, the study should alert all clinicians suspecting a patient of using cannabis too liberally to also look for subsequent affective disorders. While they are not common, this Danish survey shows that neither are they rare.