Secondary Causes of Insomnia
Insomnia is defined as difficulty falling or staying asleep, or the complaint of unrestorative/unrefreshing sleep. Most people experience short-term insomnia from time to time, but when insomnia lasts for more than several weeks, it is considered chronic and should be evaluated by a physician.
Insomnia used to be classified by sleep specialists as either primary or secondary insomnia. Secondary insomnia was insomnia that was due to an underlying medical, neurological, or psychiatric condition. Examples include insomnia secondary to depression and insomnia due to arthritis. Over the last several years, it has become increasingly recognized that in a particular person insomnia may have several different causes, and it may be impossible to determine the exact cause of the insomnia. For example, in a 55 year old man with depression, congestive heart failure, and arthritis, it may be difficult to determine whether his insomnia was due to one of his psychiatric/medical problems, or if his insomnia was primary (not due to a medical, neurological, or psychiatric disease). To further complicate matters, insomnia is a risk factor for the development of several medical and psychiatric disorders, including major depressive disorder. Therefore the term comorbid insomnia is gradually replacing the term secondary insomnia, in recognition of the fact that insomnia is often coexistent with other diseases and that the causal relationship is frequently difficult to determine.
Despite the difficulties discussed above, it is important to try and determine if insomnia may be due to an underlying condition, because treating that condition may cure the insomnia. For example, treating depression sometimes will fix the sleep disturbance associated with depression. Some secondary/comorbid insomnias have specific pharmacological treatments. The class of blood pressure medications called alpha-one blockers improves sleep in PTSD patients by reducing trauma-related nightmares. Incidentally, these anti-hypertensives also reduce symptoms of benign prostatic hypertrophy by relaxing the smooth muscle within this gland. Alpha-one blockers are especially useful medications in male Vietnam veterans with the combination of prostate problems and combat-related nightmares.
Insomnia is sometimes due to an underlying sleep disorder, such as restless legs syndrome or obstructive sleep apnea. Obstructive sleep apnea is often accompanied by complaints of unrefreshing sleep and frequent awakenings. Due to the health complications of obstructive sleep apnea, it is important to treat this condition directly rather than simply treating the associated insomnia with medications. In many cases, effective treatment of obstructive sleep apnea will cure a person's insomnia.
However, treating the "underlying condition" in cases of comorbid/secondary insomnia does not always eliminate the insomnia. In a future posts I will write more about pharmacological and behavioral treatments for insomnia. Cognitive behavioral therapy for insomnia has been successfully used to treat both primary and comorbid insomnias. Coming up next time I'll talk about problems and complications related to the use of continuous positive airway pressure (CPAP) for obstructive sleep apnea.