What came first: depress-ion or insomnia? Clinicians hold to the textbook view that depression causes insomnia, but new research suggests the very opposite, that insomnia may be a primary cause of depression, anxiety and other psychiatric disorders.
While most of us have phases of sleeplessness, the cause is often clear-a divorce, exams, job worries, even physical pain or a bedroom that's too warm at night.
But when insomnia is a persistent problem that lasts longer than six months with no obvious cause, then doctors are led to believe that it is a marker of a deeper problem, one that's often psychiatric.
Indeed, chronic insomnia has been proven to be, as psychiatrists describe it, a 'secondary condition'. In 5622 individuals aged over 15, 18.6 per cent reported some degree of sleeplessness. Of these, one-third said they suffered from anxiety, and 12 per cent had depression (Encephale, 2002; 28: 420-8).
In 14 adults with sleep problems, researchers found that the subjects' inability to sleep was associated with "stress-related intrusive thoughts" (Psychosom Med, 2000; 62: 227-30).
Researchers at Stanford believe that the extent of the disorder determines the degree of insomnia, and that chronic insomnia may also be a residual symptom from a pre-vious mental disorder. They based their conclusions on an analysis of 14,915 subjects, 19 per cent of whom reported some degree of insomnia and 90 per cent of whom had some other chronic problem. Of the latter, around 28 per cent had a psychiatric disorder, and 25 per cent had a history of such problems (J Psychiatr Res, 2003; 37: 9-15).
Insomnia as a first cause
Yet, a growing minority of research-ers believe that insomnia came first, that it is a cause of depression and anxiety. Researchers from the Sleep Disorders and Research Center in Detroit reckon that insomnia may be a cause, rather than a symptom, of psychiatric problems in up to 25 per cent of chronic cases (Clin Cornerstone, 2003; 5: 5-15).
This finding is supported by studies where people with insomnia had no anxiety or depression. The researchers concluded that insomnia may be an indicator of those who are at greater risk of developing anxiety disorders (Sleep, 2007; 30: 873-80).
But there's even new research that suggests that insomniacs don't have a psychiatric problem at all. Instead, the lack of sleep is causing them to be overemotional. Research-ers at the University of California at Berkeley found that sleep depriva-tion can cause the amygdala-the part of the brain that governs the emotional response-to become overactive (Curr Biol, 2007; 17: R877-8).
What causes insomnia?
If insomnia isn't always caused by depression or anxiety, then whydoes it happen? It's a multifactorial problem that is associated with age, gender-more women than men are sufferers-poor physical health, inactivity, and the use of tranquil-lizers and sedatives such as benzo-diazepines (J Am Geriatr Soc, 1997; 45: 1-7).
One prevailing view is that it is the result of hyperarousal. Brain scans of patients who suffer from hyperarousal display higher levels of cerebral glucose metabolism both during sleep and while awake. Their inability to fall asleep may be due to a failure of the arousal mechanism in their brain to 'switch off' (Am J Psychiatry, 2004; 161: 2126-8).
This suggests that, while most of us may have insomnia occasionally, those who suffer from it chronically (for more than six months) may have a predisposition towards it.
How can it be treated?
Chronic insomnia can be caused by many things-from physical pain and emotional problems to localized environmental factors-so it's important to first establish why it's happening. Doctors may be too quick to prescribe a tranquillizer, which can have a paradoxical effect and cause sleeplessness.
Non-drug therapies appear to be more successful, as researchers from the VA Medical Center in Durham, North Carolina, have discovered. They tested relaxation therapy and cognitive behavioural therapy (CBT) on a group of 75 people with chronic insomnia that apparently had no obvious cause.
While both types of therapy helped to improve the patients' sleep patterns, CBT was by far and away the more successful. Those receiving CBT reported a 54-per-cent reduc-tion in sleeplessness compared with only 16 per cent in the relaxation group, and they also achieved six hours of uninterrupted sleep (JAMA, 2001; 285: 1856-64).
The three levels of insomnia
- Transient insomnia: This is the type that most of us suffer from at one time or another. It can last for up to a week, and clinicians prefer to call it 'adjustment sleep disorder', as it's usually associated with a change of circumstances such as a new job, or an upcoming deadline or exam.
- Short-term insomnia: This type can last from one to six months, and is associated with a more persistent, or deeper, situation such as a death, illness or divorce.
- Chronic insomnia: This affects around 10 per cent of the adult population, and is a form of sleeplessness that lasts longer than six