Independent or Substance-Induced Mental Disorders? An Investigation of Comorbidity in an Acute Psychiatric Unit

Abstract

Objective: The comorbidity of substance use disorders and mental disorders calls for instruments designed to disentangle the complex interactions that exist when these conditions co-occur. Targeted treatment is dependent on diagnostic accuracy. The aim of this study was to differentiate independent from substance-induced mood and psychotic disorders in patients hospitalized with substance use and mental disorders. Methods: Fifty-eight patients admitted to an acute psychiatric unit with substance use and presenting mood symptoms, psychotic symptoms, or both, were interviewed with the semi-structured Psychiatric Research Interview for Substance and Mental Disorders (PRISM). Substance use disorders and other mental disorders (independent and substance-induced) were registered. Results: Seventy-one percent were men, and median age was 33 years. The substances most often heavily used were alcohol (71%), cannabis (52%), and stimulants (38%). The four most common current diagnoses were major depressive episode (50%), schizophrenia (21%), manic episode (10%), and mood disorder with psychotic symptoms (9%). Forty percent of the participants had current substance-induced mood or psychotic disorders. Current major depressive episode was substance-induced in 72% of patients with this diagnosis, of which 57% were alcohol-induced. Current schizophrenia was substance-induced in 1 of 12 patients with schizophrenia and current non-schizophrenia psychotic disorders were substance-induced in 5 of 7 patients with this diagnosis. Conclusions: The majority of current major depressive episode was substance-induced, most often alcohol-induced. Current psychotic disorders were substance-induced in approximately one-third of cases. Diagnostic accuracy in an acute psychiatric unit is important for targeted treatment.

Keywords:

• PRISM
• comorbidity
• dual diagnosis
• substance-related disorders
• mood disorders
• psychotic disorders
• substance-induced disorders

ACKNOWLEDGMENTS

This study was supported by the Regional Centre of Excellence for Dual Diagnosis Substance Abuse and Mental Illness in Health Region South-East, Norway. We thank Katinka Anchersen and Tone Lykke-Enger for their contribution in the translation of PRISM into Norwegian. We are thankful to Rune Tufte because of his continuous optimism and support during the whole project period and to Trine Asskildt for facilitating the screening process. Finally we thank the staff in the acute unit for always collaborating in an optimal way to make psychiatric research possible in their busy clinical work situation.