In the Porsolt forced swim test, nNOS KO mice showed decreased depression-related behavior [Fig 2A–C; genotype effect, first trial: F(1,28) = 9.660, p = 0.0043, a day after the first trial: F(1,28) = 18.554, p = 0.0002, 7 days after the first trial: F(1,28) = 8.263, p = 0.0076]. This evidence concerns the gene NOS1 and depressive disorder.