In major depression, risk factors associated significantly with an increased risk of moderate to severe OSA and obtained by the method of automatic selection (stepwise backward) were male gender, snoring, ESS score > 10, ISI score < 15, metabolic syndrome, age ≥ 50 years, BMI >30 kg/m2, ferritin >300 μg/L, CRP >7 mg/L, and duration of sleep ≥8 h. Here, CRP is linked to major depressive disorder.