People with major depressive disorder (MDD) are more than 10 times more likely to have cannabis use disorder (CUD) than the general population, according to a major new study analysing data from over 3 million participants.
The meta-analysis, published in the Journal of Psychiatric Research, found that 31.12% of those with CUD also had MDD, whilst 10.13% of those with MDD were dealing with CUD – compared to less than 0.3% in the general population. The link works bidirectionally, meaning high rates of co-occurrence exist regardless of which condition develops first.
The multinational team of researchers said that despite the simultaneous occurrence of substance use and depression being observed by scientists for decades, there was a lack of evidence detailing how frequently it occurred.
The study also found that the strength of the link between CUD and MDD differed significantly when tested in the community compared with tests conducted within a psychiatric hospital setting.
The team collated and analysed data from 55 international studies involving more than three million participants. To identify the relevant studies, they used the PRISMA method to search for published studies investigating the prevalence of MDD in CUD patients and the prevalence of CUD in MDD patients. The studies included data from the US National Inpatient Sample (NIS) and the Danish Civil Registration System.
Researchers used advanced statistical models known as meta-regressions to analyse large datasets and account for differences in study methods and participant demographics.
The study also discovered significant differences in the number of diagnoses of CUD within different settings. Diagnoses of CUD made within a community setting – defined as individuals coming from the general population, including hospital outpatient visits and doctors’ surgeries – were much lower in number than those diagnosed in a psychiatric hospital setting, leading scientists to advise for more CUD testing in psychiatric settings.
“Psychiatric populations demonstrated consistently higher prevalence than community samples across diagnostic periods, reflecting the greater severity and psychiatric comorbidity typically observed in treatment-seeking individuals with CUD,” the study authors wrote.
The study concluded that rates of CUD are significantly higher in people with MDD than in the general population, with the relationship working in both directions. The researchers also found that the two disorders don’t necessarily occur simultaneously.
“Finally, these findings emphasize the importance of addressing both conditions concurrently in clinical and research settings. While pharmacological treatments for comorbid CUD and MDD remain inconclusive, psychological interventions such as Cognitive Behavioral Therapy (CBT) and Motivational Interviewing (MI) show promise and warrant further investigation,” the study authors said.
