Insomnia: Symptom or Disorder?

Insomnia is the most common sleep disorder and is one of the most common symptoms reported by patients with both medical and psychiatric illnesses. Population-based estimates indicate that about 33% of the adult population reports insomnia symptoms and 10 – 15% report daytime impairment in functioning as a result (APA, 2013). This, of course, raises the issue of whether or not insomnia is a separate disorder in its own right or if it is, in fact, just a symptom of other medical or psychological problems. This leads to a diagnostic problem faced by health care professionals regarding how best to understand insomnia. Diagnosis should have a meaningful impact on treatment, so ultimately the resolution of this problem directly bears on the quality and type of care given to individuals suffering with the inability to sleep. So we have to ask, is insomnia a symptom of another disorder, such as major depression, or is it a disorder in its own right that might even be a causal factor in the development of an illness such as major depression?

Until recently insomnia was conceptualized as consisting of a number of subtypes, all of which were characterized by difficulty in the initiation and maintenance of sleep that resulted in daytime symptoms like fatigue and poor memory (Thorpy, 2012). Under the International Classification of Sleep Disorders Second Edition (ICSD-2, American Academy of Sleep Medicine, 2005) the following insomnia types were recognized: Adjustment Sleep Disorder (insomnia due to a specific stressor), Psychophysiologic Insomnia (due to increased arousal and learned maladaptive sleep patterns), Paradoxical Insomnia (patients experience getting less sleep than they objectively appear to), Idiopathic Insomnia (insomnia that started in and has persisted since childhood), Insomnia Due to a Mental Disorder (when the insomnia is a part of a disorder such as major depression), Inadequate Sleep Hygiene (insomnia due to behaviors which are inconsistent with good sleep such as having irregular bedtimes and rise times), Behavioral Insomnia of Childhood (Sleep-Onset Association Type in which a child requires inappropriate conditions to be able to sleep such as having a light on all night, Limit-Setting Sleep Type in which children stall going to bed and that is not addressed effectively by a care giver, and Combined Type that has aspects of both), Insomnia Due to Drug or Substance (such as cocaine), and Insomnia Due to Medical Condition (when the cause of the insomnia is considered to be a medical disorder such as chronic pain). These subtypes of insomnia were further considered to be either primary, in that they were not due to another disorder, or secondary when the insomnia was believed to be due to another medical disorder (e.g. heart disease), psychiatric disorder (e.g. an anxiety disorder), or another sleep disorder (e.g. sleep apnea).

Research has generally failed to support these subtypes of insomnia as distinct phenotypes. Both research and clinical experience have indicated that it is best to consider insomnia to be an independent problem area with potential bidirectional causality in that it can both be the cause of and the result of other disorders (Seow et al, 2018). This kind of reasoning has recently had an impact on diagnosis in sleep medicine, psychiatry, clinical psychology, and general medicine. Several revisions of the diagnostic nosology have been completed in recent years that reflect these changes. With the Diagnostic and Statistical Manual Fifth Edition (DSM-5, American Psychiatric Association, 2013) and the International Classification of Sleep Disorders Third Edition (ICSD-3, American Academy of Sleep Medicine, 2014), the above distinctions between subtypes of insomnia have been dropped and a diagnosis of insomnia disorder can be made alone or as a co-morbid condition with another medical, psychiatric, or sleep disorder, as the case may be. This is a major shift in the diagnosis of insomnia and was based on the difficulty of establishing any reliable cause/effect relationship between insomnia and other medical or psychiatric disorders (Sateia, 2014).

This has implications for treatment. Primarily, it indicates that insomnia should be evaluated and treated, even if there are other disorders present. For example, rather than just treat depression and hope that the attendant insomnia clears up, specific attention should be paid to the insomnia itself. This could mean selecting antidepressants with soporific effects, adding a sleeping medication, or perhaps best of all, providing cognitive behavioral strategies to the patient to help with management of the insomnia problem.

A recent study by Seow et al (2018) investigated the relationship between insomnia and psychiatric disorders. The study was conducted in Singapore and used insomnia criteria from the DSM-5 (APA, 2013). Participants were adults seeking psychiatric treatment at the Institute of Mental Health in Singapore. This is the main psychiatric hospital in Singapore and 400 patients between the ages of 21 and 65 were included in the study. There were 100 patients with major depressive disorder, 80 with bipolar disorder, 100 with anxiety disorders, and 120 with schizophrenia or schizoaffective disorder. Of these patients, 31.8% (127 of the 400 patients) met DSM-5 criteria for insomnia disorder. Nearly half (45.0%) of the patients with major depressive disorder and a third (33%) of those with anxiety disorders also met criteria for insomnia. Fully 50% of the patients (200) reported that they had sought treatment for insomnia from a health care professional. Only 12% (24) of the patients were given any form of sleep hygiene education or any psychotherapeutic intervention specifically to help the insomnia. Most (182 patients or 91% of the 200) were prescribed sleeping medication. Of these 74.2% (135 patients) found the medications to be at least somewhat helpful but they also had many concerns such as fear of dependence on them, daytime hangover, and decreased effectiveness over time.

Interestingly, while the patients with insomnia had greater impairment than patients who did not meet criteria for insomnia disorder in terms of functioning, fatigue, and sense of well-being, there were no differences observed in terms of use of treatment services such as emergency care, outpatient treatment, hospitalization, or psychotherapy. Those with insomnia were statistically different in that they were more often unemployed, had lower activity levels, used more sleeping medication, and more often had an additional, secondary psychiatric comorbidity.

Insomnia appears to make treatment of psychiatric disorders more difficult but a lower priority seems to have been set by clinicians for the insomnia symptoms than for other psychiatric symptoms. The implication is that there is a lack of diagnosis and treatment of insomnia in this population of patients. It is unlikely that conditions are different in the United States. While this study was limited by only considering one treatment setting and had a limited set of psychiatric disorders that were evaluated, it nevertheless does begin to show how common insomnia is among patients seeking treatment for psychological disorders and how limited the treatment approaches are that have been available for addressing it. It is also clear that much more attention needs to be given to the potential benefits of providing cognitive and behavioral therapy for insomnia to patients seeking psychiatric treatment who also meet criteria for insomnia.