Affective instability in those with and without mental disorders: A case control study

Background Affective instability (AI) is transdiagnostic, and associated with suicidality and healthcare use. It has rarely been compared between diagnoses or to controls. We investigated: whether AI differs between clinical cases and controls and between diagnoses; how different AI components are correlated; and whether AI is associated with functioning in clinical cases.

Methods Cases (N = 69) from psychiatric services had a diagnosis of borderline personality disorder, bipolar disorder, major depression or psychosis and were compared to primary care controls (N = 25). Participants completed the affective lability scale (ALS), affective intensity measure (AIM), affective control scale (ACS), scored mood fluctuation rate and the WHO-DAS.

Results There was a significant difference in affective lability between cases and controls and across diagnostic groups (p < 0.001). Compared to controls, cases showed lower affective control (p < 0.05). There were no differences in affective intensity between cases and controls or between diagnostic groups, or in mood fluctuation rate between groups. ALS score (p < 0.001), and total number of medications (p < 0.046), were associated with functioning, independent of diagnosis.

Limitations The sample size was modest. Cases were not in an acute illness episode and this could bias estimates of group difference towards the null.

Conclusion Individuals with mental disorder demonstrate higher levels of affective lability and lower affect control than those without mental disorder. In contrast affective intensity may not be useful in demarcating abnormal affective experience. Independent of diagnosis, affective instability, as measured by affect lability, adversely impacts day-to-day functioning. It could be an important target for clinical intervention.