Diminished perception of ambient light: a symptom of clinical depression?

In a non-randomized, uncontrolled pilot study, the authors investigated whether depressed patients were more likely to perceive the lighting in their environment as being dimmer than usual.

120 patients (46 males, 74 females) who presented for possible admission for depression at a psychiatric facility were administered a Diagnostic and Statistical Manual of disorders (DSM-IV) based questionnaire and underwent psychiatric evaluation. A question asking whether 'the lights in my surroundings seem dimmer than usual' was included in the 15-point question survey. Statistical analyses were performed to determine whether an affirmative response to this dimness question was correlated with the depth of depression (mild, moderate, severe) and also whether significant correlation was present between the percentage of patients answering yes to the dimness question versus the number of yes responses to the core symptoms of depression.

Two thirds of the patients categorized as severely depressed responded that their ambient environment appeared dimmer than usual compared to 21% of moderately and 14% of mildly depressed patients. This difference was statistically significant (P<0.05). The degree of depression as determined by the number of core questions answered affirmatively and the presence of this 'dimness' symptom were highly correlated (P=0.002, R=0.87).

The specificity of the finding has not been tested in reference to non-affective psychiatric patient groups.

A patient's perception of the ambient light in the environment being dimmer than usual may be an important symptom of a major depressive disorder. Further replication and objective testing of visual function in depressed patients appears warranted.