Substance use and symptoms of mental health disorders: a prospective cohort of patients with severe substance use disorders in Norway

BACKGROUND: There is high co-occurrence of substance use disorders (SUD) and mental health disorders. We aimed to assess impact of substance use patterns and sociodemographic factors on mental health distress using the ten-item Hopkins Symptom Checklist (SCL-10) over time. METHODS: Nested prospective cohort study of 707 participants with severe SUD across nine opioid-agonist-therapy outpatient clinics and low-threshold municipality clinics in Norway, during 2017–2020. Descriptive statistics were derived at baseline and reported by means and standard deviation (SD). A linear mixed model analysis was used to assess the impact of substance use patterns and sociodemographic factors on SCL-10 sum score with beta coefficients with 95% confidence intervals (CI). RESULTS: Mean (SD) SCL-10 score was 2.2 (0.8) at baseline with large variations across patients. We observed more symptoms of mental health disorders among people with frequent use of benzodiazepines (beta 3.6, CI:2.4;4.8), cannabis (1.3, CI:0.2;2.5), opioids (2.7, CI:1.1;4.2), and less symptoms among people using frequent stimulant use (− 2.7, CI:-4.1;-1.4) compared to no or less frequent use. Females (1.8, CI:0.7;3.0) and participants with debt worries (2.2, CI:1.1;3.3) and unstable living conditions (1.7, CI:0.0;3.3) had also higher burden of mental health symptoms. There were large individual variations in SCL-10 score from baseline to follow-up, but no consistent time trends indicating change over time for the whole group. 65% of the cohort had a mean score > 1.85, the standard reference score. CONCLUSIONS: People with SUD have a considerable burden of mental health symptoms. We found no association between substance use patterns and change in mental health symptoms over time. This could suggest that the differences observed were indicating flattening of effects or self-medication to a larger degree than medication-related decline in mental health. This call for better individualized mental health assessment and patient care. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13011-021-00354-1.