- History of psychiatric disorders (confounds effect of light treatment, per relevant items from Mood Disorder, Psychotic Screening and Substance Use Disorders Modules of the Structured Clinical Interview for DSM-IV Axis I Disorders - Non-Patient Edition (SCID-IV/NP) to screen for schizophrenia, bipolar depression, substance abuse, suicidal ideation, obsessive compulsive disorder, PTSD), depressive symptoms using the Center for Epidemiologic Studies - Depression (CES-D) scale