Major Depressive Disorder (MDD) is a serious psychiatric disorder that affects more people globally than any other psychiatric disorder. A growing number of studies show that problems with emotional experience and regulation are important for understanding MDD risk. Meanwhile, people who often deal with their emotions using unhealthy strategies like hiding their emotions or ruminating over situations, are also more likely to get MDD.
Recent studies suggest that affective instability, another aspect of emotion, might also be important to consider. Affective instability describes how often someone’s emotions change and how intense those emotions are. Someone high in affective instability might be feeling intense anger one minute and then quickly shift to feeling intense sadness the next. On the other hand, someone low in affective instability would have more consistent and stable experiences of anger and sadness. High affective instability is characteristic of many various disorders, such as bipolar disorder and borderline personality disorder, but it also seems to be characteristic of MDD. People who have MDD have higher affective instability than people who do not have MDD, and people who have higher affective instability have more severe depressive symptoms.
We were interested in replicating this association between affective instability and MDD in a sample of older adults. Most studies on MDD focus on adolescents or young adults, perhaps because MDD is more common in this population. However, it is still important to study MDD in older adults since it is still the most common mental health disorder in older adults. Compared to younger adults with MDD, older adults with MDD have poorer outcomes, are less likely to recover from MDD, and more likely to commit suicide.
Interestingly, affective instability goes down with age, as does MDD prevalence. Therefore, it might be that decreased affective instability leads to decreased MDD prevalence in older adulthood. At the same time, it might be that the older adults who remain high in affective instability are the ones who end up having MDD. In addition to testing this hypothesis, we wanted to know whether affective instability can predict MDD’s course over time. Specifically, we wanted to know whether affective instability is not only useful for identifying who has MDD, but also who will recover from MDD.
To test these ideas, we conducted a 5-year longitudinal study with 1,630 adults, ages 55-64 years, in St. Louis, Missouri. At three time points, we gathered surveys from participants, someone close to the participants, and a clinician to assess participants’ affective instability. We also administered a computerized interview to assess whether they ever had MDD. Meanwhile, across eight time points, we had participants complete a survey of their depressive symptom severity.
We found that people higher in affective instability at the beginning of the study were more likely to have experienced a major depressive episode at some point in their life, and had higher depressive symptoms throughout the study. We were also able to use affective instability to predict whether someone was experiencing a major depressive episode for the first time. Affective instability was not related to how likely someone’s depressive symptoms increased over time or whether someone recover from MDD .
In sum, we found that affective instability remains an important risk factor for depression in older adulthood. For the first time, we found that affective instability can even predict a first-time major depressive episode. Interestingly though, affective instability was unrelated to recovery from a major depressive episode. Therefore, it will be important for future studies to consider how different types of factors affect a major depressive episode onset versus recovery. Overall, our findings suggest that affective instability is most relevant for the onset of depression and that it should be targeted through MDD prevention efforts.