What Can Retinal Abnormalities Tell Us About Major Depressive Disorder?

A review in the Journal of Psychiatric Research provided further evidence that retinal abnormalities detected through objective electrophysiological measurements may help identify the pathogenesis of major depressive disorder (MDD) and possibly other psychological conditions.

Because the retina is considered part of the central nervous system, it is considered an appropriate site to investigate mental illnesses. Studies investigating the retina as a predictor of psychological disorders date back at least two decades. Recent research on retinal imaging has focused on schizophrenia. A 2013 study in the American Journal of Psychiatry found that among other microvascular abnormalities, wider venules were linked to a higher risk for psychosis symptoms in both adulthood and childhood, indicating a possible distinguishing feature of schizophrenia that manifests early in life. That study, which controlled for confounding health conditions, suggested that wider retinal venules are not simply an artifact of co-occurring health problems in schizophrenia patients but were also associated with a dimensional measure of adult psychosis symptoms and with psychosis symptoms reported in childhood.

That same year, a United Kingdom study also found that simple tests focusing on viewing patterns could detect eye-movement abnormalities associated with schizophrenia from healthy controls with up to 98.3% accuracy. The current study found that retinal abnormalities can be easily and non-invasively detected with objective electrophysiological measurements such as the flash electroretinogram, the pattern electroretinogram and the electrooculogram in patients with MDD.

Beyond gaining a better understanding of the pathophysiology of MDD, the researchers believe that different types of retinal scanning hold the potential for not just predicting likelihood of suffering from MDD and other psychological disorders, but may have other significant benefits as well. In particular, according to the study results, flash electroretinogram may serve to monitor drug response in depressed patients, and pattern electroretinogram may be used to differentiate between depressed patients and controls.

The study fits nicely with recent research on monoamine neurotransmitter disorders, which consist of a heterogeneous group of neurological syndromes characterized by primary and secondary defects in the biosynthesis, degradation, or transport of dopamine, norepinephrine, epinephrine, and serotonin. Many neurotransmitter disorders mimic the phenotype of other neurological disorders (eg, cerebral palsy, and parkinsonian syndromes) and are, therefore, frequently misdiagnosed. If major depressive disorder can be definitively linked to defects or degradation in the transport of the dopamine, epinephrine, and serotonin through retinal scanning or by other means, it can perhaps be treated through the use of monoamine analogues, inhibition of monoamine degradation, or, conversely, promoting monoamine production.

The study authors hope the findings will lead to further study establishing that objective retinal electrophysiological measurements may eventually become relevant tools to investigate the pathophysiology of MDD.