1 - (IOP 36) Tired and Sad: Affective Overlap Between Sadness and Tiredness in Depression

Depression is a prevalent mental health presentation characterized by low mood and/or loss of enjoyment or pleasure. Two of the core characteristics of depression are heightened attention to negative somatic stimuli, such as aches, pains, and other unpleasant bodily sensations, and increased fatigue, which may be due in part to sleep disturbance associated with depression. Combining these observations—depressed people's heightened attention to bodily sensations and their elevated fatigue and sleep disturbance—suggests that people with depression likely perceive themselves as more tired than others, even objective sleep quality is comparable. Prior research supports this, and suggests the negative cognitive style associated with depression likely distorts sleep perception and subjective tiredness. However, it remains unclear whether these associations represent stable traits (people who are generally more depressed always rate themselves as more tired) or transient states (people rate themselves as more depressed in moments that they are more tired).

The emotion granularity hypothesis suggests people vary in their ability to precisely distinguish between different emotional states. People with major depression typically demonstrate lower emotion granularity than non-depressed controls, particularly when describing negative emotions, meaning they tend to report negative mood states in tandem. The emotion granularity theory would suggest that depressed individuals may experience tiredness (heaviness in limbs, difficulty concentrating) and misattribute those sensations to their emotional state due to difficulty distinguishing between physical fatigue and emotional distress. Additionally, these patterns may be confounded or exaggerated if tiredness is interpreted as hedonically unpleasant in depressed individuals, due to the heightened attention to unpleasant bodily sensations, and results in additional affective experiences of sadness.

To understand how depression and tiredness relate dynamically, it is necessary to study these relationships in real time. No study has specifically examined the dynamic relationship between momentary ratings of depression and tiredness using a within-person EMA design. The study presented in this oral presentation examines 665 college students recruited for a separate, large EMA study. Depression severity was measured at baseline, and momentary affect (“sad” and “tired”) were collected over an EMA period of 8-weeks (80,878 EMA observations were collected across the sample). Initial results of a multi-level moderated model indicate that the association between momentary sadness and momentary tiredness is stronger in individuals with higher levels of baseline depression. This finding suggests that the perception of tiredness, and in turn sleep disturbance, may have important implications for the emotional experiences of individuals with major depression.