Mental health disorders, such as depression, seasonal affective disorder (SAD; via a Pro10Leu mutation in a related opsin gene, OPN4; Roecklein et al., 2009), anxiety, schizophrenia, bipolar disorder, Alzheimer’s disease, and other forms of dementia are associated with photosensory disruption (Foster et al., 2013). Here, OPN4 is linked to early-onset autosomal dominant Alzheimer disease.