Background There is a lack of studies on the course and effectiveness of
medical cannabis in the treatment of major depressive disorder (MDD).
Methods Retrospective longitudinal (18 weeks) study of n=59
outpatients with MDD, treated with medical cannabis via a telemedical platform.
Previous treatment with antidepressant medication was required for inclusion
into the study. Standardized data collection was carried out at entry and during
monthly consultations. Severity of depression was measured on a 0–10
point rating scale. Side-effects were assessed by a checklist.
Results Patients were 20–54 years old; 72.9% were male;
one third reported times of regular cannabis consumption within the previous
five years. Drop-out rate was 22% after 18 weeks. Mean severity of
depression decreased from 6.9 points (SD 1.5) at entry to 3.8 points (2.7) at
week 18 (baseline observation carried forward; 95% CI for the mean
difference: 2.4 to 3.8; p<0.001). A treatment response
(>50% reduction of the initial score) was seen in 50.8%
at week 18. One third of patients complained about side effects, none was
considered as severe. Concomitant antidepressant medication (31% of
patients) was not associated with outcome.
Conclusions Medical cannabis was well tolerated and dropout rate was
comparable to those in clinical trials of antidepressant medication. Patients
reported a clinically significant reduction of depression severity. Further
research on the effectiveness of medical cannabis for MDD seems warranted. Risks
of this medication, such as sustaining or inducing a cannabis use disorder, or
side effects such as poor concentration, must be taken into consideration.