Medical conditions and medications
A number of medical conditions (and/or medications that are used to
treat them) can impair sleep. As seen in Table 2.1, a variety of medical
problems are commonly comorbid with insomnia and may, at least partly,
cause difficulty sleeping [38]. For example, hyperthyroidism can result
in significant insomnia, and patients should generally be tested for this
when being evaluated for insomnia. As mentioned earlier, although
insomnia is often precipitated by a medical disorder, the insomnia often
decouples and evolves into an independent, self-sustaining problem that
can have a reciprocal exacerbation of the medical disorder.