Longitudinal course and characteristics of cyclothymic disorder in youth

Epidemiological studies suggest that cyclothymic disorder is the most prevalent subtype of bipolar disorder (BD). However, it is rarely diagnosed, especially in youth. This may be because it can be difficult to ascertain whether a youth meets diagnostic criteria. Clearer, easy-to-apply criteria could reduce misdiagnosis. The objective oftable this study was to determine whether proposed research diagnostic criteria for cyclothymic disorder (RDCyc), based on DSM-5 criteria, could be quantified and validated in youth.

Participants from the Longitudinal Assessment of Manic Symptoms (LAMS) study were recruited based on symptoms of mania and followed prospectively. RDCyc criteria were: 1) At least one core symptom each of mania and depression; 2) one additional symptom of mania and of depression; 3) persistence over two consecutive six-month periods, and 4) impairment. Exclusionary criteria were having a [hypo]manic or depressive episode. Outcomes at the two-year follow-up were compared between RDCyc youth and other diagnostic groups (BD I/II, BD NOS/non-RDCyc cyclothymic disorder, disruptive behavior disorders [DBD], depression).

Thirty-seven youth met RDCyc criteria. There were no consistent differences between the RDCyc youth and youth with other BD subtypes (ps=0.001-0.960, with all-but-one p value >0.02). RDCyc youth had higher depression (p<0.0005) and mania scores (p=0.001), lower functioning (p=0.012), and higher suicide risk than DBD youth (p=0.001). They had higher mania scores than depressed youth (p.018).

The majority of youth in the sample were recruited due to elevated symptoms of mania, which may limit the generalizability of the results. Youth were followed for two years, which may not be long enough to determine whether or not they will eventually develop a manic or depressive episode.

Applying RDCyc criteria identified youth who were similar to others with BD and were more impaired than those with DBD. Using these criteria could reduce misdiagnosis and increase our understanding of this prevalent, but largely ignored, diagnosis.