Major depressive episodes are associated with altered cortical processing of visual contrast for some patients, according to research published in the Journal of Psychiatry and Neuroscience.
The investigators recruited individuals for a healthy control group (n=29) as well as patients (n=111) in Finland between 2013 and 2016. They assessed the study participants for visual processing via brightness induction and contrast suppression tests using a 1-interval adaptive staircase method and a 2-alternative forced-choice task. At 7 months, 74 patients were reassessed.
The patient cohort comprised individuals with unipolar major depressive disorder (MDD; n=46), bipolar disorder (BD; n=38), and borderline personality disorder (BPD; n=27). The MDD, BD, BPD, and individuals in the control groups comprised 58.7%, 71.1%, 74.1%, and 72.4% women and had mean ages of 31.8±10.1, 32.0±9.3, 28.0±7.3, and 32.1±9.0 years, respectively.
No significant differences were observed between patients and individuals in the control group during the brightness induction test (t[39.8], 0.534; d, 0.115; P =.60). The investigators did detect significant group differences for the contrast suppression test (t[35.2], 2.902; d, 0.663; P =.006), in which patients had significant orthogonal differences (t, 2.80; P =.006) but not collinear differences (t, 1.55; P =.12).
These observations indicated that patients had reduced contrast suppression, the illusion was less strong, and stimuli were perceived more veridically than in participants in the control group.
Group differences could not be explained by a model including age, gender, patient subgroups, medication use, extroversion, conscientiousness, neuroticism, agreeableness, openness, or alcohol consumption (F[11,80], 1.105; R2, 0.132; P =.37).
Brightness induction was modestly increased and contrast suppression decreased by the use of mood stabilizers (F[1,104], 6.024; η2, 0.053; P =.016). However, the pairwise comparison was not significant (contrast suppression: t[17.26], -2.095; P =.051; brightness induction: t[16.46], 1.269; P =.22).
At the 7-month follow-up, 56.4% of the MDD, 60.6% of the BD, and 52.2% of the BPD cohorts were in remission from their major depressive episode. At the reassessment, depressive scores were not significantly correlated with brightness induction (r, 0.073; P =.556) or contrast suppression (r, -0.156; P =.189).
This study was limited by the potential influence of behaviors on the results of visual tests and the fact that retinal and cortical processing were indirectly inferred.
Salmela V, Socada L, Söderholm J, et al. Reduced visual contrast suppression during major depressive episodes. J Psychiatry Neurosci. 2021;46(2):E222-E231. doi:10.1503/jpn.200091