In a sample of 254 adult men recruited from a manufacturing company, self-reported insomnia (defined as the perception of poor sleep combined with either difficulty falling asleep, difficulty maintaining sleep, or waking up too early one or more times during the past year) was associated with lower stimulated IFN-γ production and a lower IFN-γ/IL-4 ratio in the absence of other medical disorders (484). Here, IFNG is linked to insomnia.