Because obstructive sleep apnea disrupts sleep and causes multiple awakenings, some patients with obstructive sleep apnea report insomnia. However, it also causes daytime sleepiness, and many patients describe excessive sleepiness. This model is similar to how fatigue presents in psychiatric disorders. Some patients complain of depression, mood swings, anxiety, irritability, or panic attacks and seek therapy or medications for these symptoms. However, each of these symptoms is strongly associated with fatigue. This article describes sleepiness and fatigue commonly seen in psychiatric disorders.