Association between a Serotonin Transporter Length Polymorphism and Primary Insomnia

STUDY OBJECTIVE: To test the hypothesis that a 44-base-pair insertion/deletion polymorphism in the 5' regulatory region of the serotonin transporter gene (5-HTTLPR) is associated with primary insomnia. DESIGN: Association study. SETTING: Sleep laboratory at the Central Institute of Mental Health, Mannheim, Germany. PATIENTS: 157 patients with primary insomnia and 827 healthy controls. INTERVENTIONS: N/A. MEASUREMENT AND RESULTS: We found the short (s-) allele of the 5-HTTLPR to be significantly more frequent in patients suffering from insomnia than in control individuals (47.1% vs. 39.9%: OR = 1.34). CONCLUSIONS: This finding contributes to the understanding of the pathophysiology of primary insomnia and suggests a biological basis between the prevalent comorbidity of primary insomnia and other psychiatric disorders.