Background: There is extensive evidence, from both clinical cases and rodent models, for reduced levels of the widely expressed neuropeptide Y (NPY) in anxiety and depressive disorders. The rare allele of the Leu7Pro polymorphism in the signal peptide of preproNPY has been associated with higher processing into mature NPY, and higher NPY levels in plasma and cerebrospinal fluid. The Pro7 allele was proposed to protect against depression in a small Swedish clinical sample (Heilig M., Zachrisson O., Thorsell A., Ehnvall A., Mottagui-Tabar S., Sjögren M., Asberg M., Ekman R., Wahlestedt C., Agren H., 2004. Decreased cerebrospinal fluid neuropeptide Y (NPY) in patients with treatment refractory unipolar major depression: preliminary evidence for association with preproNPY gene polymorphism. J. Psychiatr. Res. 38, 113-121).
Method: Leu7Pro was analyzed in a large well-characterized longitudinal population-based sample of adult Swedes with data on life situation and life history, including 461 with depression diagnosis, 157 with anxiety diagnosis and 1514 healthy individuals with no symptom of psychopathology.
Results: Pro7 was rarer in depression cases than in healthy individuals (OR=2.7; P=0.0004). The protective effect of Pro7 was similar despite exposure to known environmental vulnerability factors. Pro7 appeared with similar effect size in those with an anxiety diagnosis, but this was not statistically significant (OR=2.3; P=0.06).
Limitation: The size of the anxiety sample and possibly some recall bias of childhood conditions.
Conclusion: Pro7 allele of preproNPY protected against depression among Swedes. Pro7 is not common, but was found to exert its protective effect also in an environment-induced vulnerable state. This supports a protective effect of NPY in line with previous reports suggesting anxiolytic-like and antidepressant-like effects of NPY.