How are sleep and mental disorders related?

Sleep problems are extremely common in the general population and in people with affective disorders. Epidemiological data suggest that up to 35% of adults suffer from insomnia over the course of a year, with 9%-17% of them having insomnia that is persistent and bothersome.

It is widely accepted that sleep disruption is a symptom of an underlying psychiatric disorder. For example, in the Diagnostic and Statistical Manual of Mental Disorders (5th edition) (DSM-5), insomnia is a diagnostic criterion or clinical feature of several psychiatric disorders. Difficulty falling asleep is usually associated with anxiety conditions, while early awakening is generally considered a typical vegetative neurological symptom of depression. Insomnia is quite common even in patients with active psychosis. In patients with bipolar disorder, the manic phase is typically characterized by a reduced need for sleep, whereas hypersomnia is more common in the depressive cycle. Conversely, some evidence also suggests that chronic insomnia (rather than a symptom of psychiatric illness), often leads to psychological symptoms such as irritability, nervousness, irritability, and possibly increased susceptibility to depression. Although there is evidence of a relationship between the severity of sleep disorders and psychopathology, clear evidence of a causal relationship is still lacking. So, how exactly are sleep disorders and psychopathology related?

Is there a relationship between sleep and psychiatric disorders?

1. The proportion of sleep difficulties and psychiatric disorders associated
Three large epidemiological studies investigated the proportion of co-occurring sleep difficulties and psychiatric disorders in randomly selected community samples. In the studies, 7954 community residents were surveyed about their diagnoses of sleep and psychiatric symptoms. The prevalence of psychotic syndromes was much higher among those with sleep problems. 40% of those with insomnia and 47% of those with narcolepsy were diagnosed with a psychiatric disorder, compared to 16% of those without sleep problems. Insomnia is defined as a problem falling or staying asleep for 2 weeks or more in the past 6 months that cannot be attributed to physical illness, medication or substance abuse. Although insomnia may represent a symptom of another disorder in a large proportion of the population, it may also represent a separate syndrome for most individuals with sleep difficulties.

2. Psychiatric diagnosis of patients with insomnia
Previous studies have evaluated a series of 216 patients with insomnia. 44% of patients were diagnosed with “insomnia associated with other psychiatric disorders”, while 20% were diagnosed with “primary sleep disorder”, i.e., insomnia that does not occur exclusively in the course of other psychiatric or medical disorders. medical disease process. The most common diagnoses were mood-related sleep disorders (32%), anxiety (5%), and substance-induced sleep disorders (3.5%). Although these data suggest a high rate of insomnia secondary to psychopathology, clinicians vary widely in the frequency of these diagnoses, reflecting differences among sleep specialists as to whether insomnia is considered a functional autonomic disorder or a symptom of an underlying psychiatric disorder in the strict sense.

3. Prevalence and severity of sleep complaints in psychiatric patients
Of 2512 consecutive patients who consulted their physicians for health problems, 18.2% had severe insomnia, 12.2% had moderate insomnia (but no impairment in daytime functioning), 15% reported mild insomnia (occasional difficulty falling or staying asleep), less than 1% complained of ADHD, and 53% were completely satisfied with their sleep. GPs estimated the prevalence of psychiatric disorders based on seven possible diagnoses to be 9.9% (no insomnia), 13.5% (mild), 20.7% (moderate) and 37.4% (severe), respectively. These findings suggest that the prevalence of psychiatric co-morbidity is 2-fold and 4-fold higher in patients with moderate and severe insomnia, respectively, compared to patients without sleep problems. The association between moderate/severe insomnia and depression was particularly strong.

In a survey of 100 consecutively hospitalized psychiatric patients, 80 patients suffered from sleep disorders, 72 of whom had insomnia. All but one patient complained of situational insomnia. Adjustment disorders were the most common psychological problem, followed by affective disorders and psychological factors affecting physical status. There was no difference in the rate of psychiatric diagnosis in patients with and without sleep disorders.

In conclusion, epidemiological surveys have shown a high prevalence of co-occurrence of sleep disorders and psychological symptoms in randomly selected community samples; however, they have also shown that insomnia is a separate symptom or disorder in more than half of the surveyed samples. Clinical case series studies have also shown a high rate of co-morbidity between sleep disorders and psychiatric disorders in patients with sleep disorders. Despite significant methodological differences across studies, these high estimates suggest that insomnia is strongly associated with psychopathology, particularly with depression and anxiety. A large proportion of patients who complain of insomnia and seek treatment have one or more diagnosable psychiatric disorders at the same time.

How can it be prevented?

Sleep disorders often lead to prolonged use of hypnotic medications, especially in those patients with concomitant psychological distress. First, despite the initial intent to use these medications on a short-term basis, a significant percentage of patients with moderate and severe insomnia develop dependence and continue to use hypnotic medications for an extended period of time. Early psychological intervention may prevent long-term use of and dependence on hypnotic medications and reduce health care costs. Second, if insomnia is a significant risk factor for future depression, early detection and treatment of insomnia may prevent the development of full-blown major depression. Third, sleep disruption may be a risk factor for families in older adults with cognitive impairment. Nighttime sleep disruptions can place a heavy burden on caregivers and increase caregivers’ own vulnerability to anxiety and depressive disorders. Clinical interventions to regulate sleep behaviors and schedules in patients with insomnia may reduce caregiver burden.

How to respond scientifically?

The co-occurrence of sleep and psychiatric disorders raises important questions for treatment planning and prediction of treatment response. What should be the focus of treatment? Should the two conditions be treated simultaneously or sequentially? First, when the sleep disorder is a core symptom of an underlying psychopathology (e.g., generalized anxiety or major depressive disorder), treatment should focus on the psychopathology. Second, if the sleep disorder is essentially primary, then treatment should focus primarily on sleep, followed by appropriate diagnostic testing. If sleep and psychological symptoms coexist, but there is no clear evidence of a unidirectional causal relationship, multifocal interventions targeting both symptom clusters may be needed to optimize treatment outcomes and maintain treatment effectiveness. Finally, sleep abnormalities may persist despite effective treatment of major depression, suggesting that maintenance treatment targeting sleep and other depressive symptoms may prevent future relapse.

The issue of co-morbidity in psychiatric disorders has attracted considerable clinical and research interest over the past few years. The co-morbidity of sleep and psychiatric disorders is also important for improving our understanding of psychopathology and designing more effective prevention and treatment programs. Additional clinical research data are needed to verify whether sleep disorders increase susceptibility to psychiatric disorders, whether the persistence of sleep disorders prevents or delays recovery from psychiatric disorders, and whether successful treatment of sleep disorders prevents the onset or limits the duration of coexisting psychiatric disorders.