Longitudinal Dynamics Between Anxiety and Depression in Bipolar Spectrum Disorders

Anxiety and depression are common among individuals with bipolar spectrum disorders (BSDs), with anxiety being a risk factor for depression and vice versa. While the harmful effects of these symptoms are well recognized, their temporal dynamics have not been fully tested. To address this gap, our study investigated bidirectional relationships between anxiety and depression in individuals with BSDs using data from the Prechter Longitudinal Study of Bipolar Disorder, collected over an average of 11 years. We included 651 participants with various BSD subtypes (BD I, BD II, BD not otherwise specified, and schizoaffective bipolar type), with at least 5 years' data for adequate statistical power in detecting temporal dynamics. Bimonthly measurements of anxiety and depression were analyzed using dynamic structural equation modeling. Beyond assessing autoregressive and cross-lagged effects, this study also investigated whether temporal dynamics differed based on demographic characteristics and the use of psychiatric medication. Our findings revealed that individuals with BSDs experienced significant fluctuations in anxiety and depression over time. In addition, we found significant autoregressive and cross-lagged effects of anxiety and depression. Comparison of the cross-lagged effects demonstrated that anxiety had a greater effect on subsequent depression than vice versa. Age and marital status impacted cross-lagged and autoregressive effects. Specifically, older participants had stronger temporal associations between depression and subsequent anxiety, while widowed participants exhibited a heightened impact of depression on subsequent depression. These results underscore the importance of early identification and integrative interventions aimed at addressing both anxiety and depression to mitigate subsequent symptoms in BSDs.