The association of phasic irritability (aggressive outbursts) and tonic irritability (irritable mood) to depression occurrences, symptoms, and subtypes.

Background: Research among adults has rarely differentiated between tonic irritability (i.e., irritable mood) and phasic irritability (i.e., aggressive outbursts) with respect to multiple dimensions of depression. The current study explored both tonic and phasic irritability in relation to depression severity, depression chronicity, age of depression onset, individual depressive symptom, and depression subtypes.

Methods: The study included participants (N = 5692) from the National Comorbidity Survey - Replication (NCS-R) part two. The NCS-R used lay-administered, fully standardized diagnostic interviews. The current study implemented linear models, generalized linear models, Cox proportional hazard model, and latent class regression.

Results: Both types of irritability were significantly associated with greater risk for MDD diagnosis, as well as risk for having at least one depressive symptom, early MDE onset, and MDE chronicity. Both phasic and tonic irritability were associated with greater odds of specific depressive symptoms and were differentially related to distinct depressive symptom constellations. Phasic irritability related only to severe depression. Lastly, both phasic and tonic irritability was associated with suicidal ideation, but only phasic irritability was associated with a suicide plan and attempt, above and beyond depression subtypes.

Conclusions: Both phasic and tonic irritability differentially related to almost all aspects of depression in adults. Specifically, tonic irritability showed overall stronger associations with various depressive features, whereas phasic irritability marked higher depressive severity.