Over the counter medications and products such as alcohol, decongestants, nicotine, and caffeine have also been linked to insomnia. Due to these potential contributing factors, a urine drug screen should be done on patients who present with insomnia complaints. In addition to the etiologies discussed above, insomnia may also result from some less common causes. Most cases of insomnia that are linked to breathing disorders are attributed to sleep apnea. For this reason, a thyroid function test is indicated in patients who present with complaints of insomnia.
Some patients suffer from sleep-related movement disorders.
Sometimes these movements are periodic and insignificant in terms of sleep interruption. However, some patients experience restless leg syndrome. This condition is characterized by discomfort in the legs that can only be alleviated by moving the legs and therefore, usually causes some degree of insomnia. Some individuals' circadian rhythm may be disturbed to an extent that produces insomnia. These severe disturbances are usually associated with jet lag or shift work.