Insomnia and Your Genes

If you suspect there’s a biological component to your insomnia, you’re probably right. Although talk about insomnia is mostly confined to situational triggers as well as habits and attitudes that keep insomnia alive, all models of chronic insomnia assume the existence of predisposing factors. Some of these factors may be inherited at birth.

What evidence is there for genetic involvement in insomnia, and where might it lead? A review published recently in Brain Sciences brings us up to date.

Genetic variants may be an underlying factor in insomniaIf you suspect there’s a biological component to your insomnia, you’re probably right. Although talk about insomnia is mostly confined to situational triggers as well as habits and attitudes that keep insomnia alive, all models of chronic insomnia assume the existence of predisposing factors. Some of these factors may be inherited at birth.

What evidence is there for genetic involvement in insomnia, and where might it lead? A review published recently in Brain Sciences brings us up to date.

Family and Twin Studies

The number of family studies is small—five—and one reason may be that in family studies it’s hard to tease apart genetic effects from the effects due to shared environment. But overall these studies suggest that insomnia tends to run in families. A recent study found that the children of parents with high levels of stress related insomnia were more likely to experience higher cognitive–emotional hyperarousal.

Twin studies are more numerous (20). By comparing correlations between identical twins (who share 100% of their genes) and fraternal twins (who share 50% of their genes on average) who are raised together, researchers can more easily sort out which effects are genetic and which are due to a shared environment. Based on twin studies, insomnia heritability estimates range from 22% to 59% in adults, depending on the type of study and which sleep variable was assessed (sleep duration? trouble falling asleep at the beginning of the night? subjective sleep quality?).

Recently, a large twin study by Lind and colleagues provided new evidence that

  • there is a larger genetic contribution to insomnia in women (59%) than in men (38%), and
  • in adults, insomnia heritability is stable across time.

Researchers assessed the heritability of insomnia through childhood and adolescence in another twin study. In youth, too, they found that genetic influences on insomnia are stable across time.

Studies of Candidate Genes

The one drawback of twin studies is that they don’t point to which genes confer vulnerability to (or protection from) insomnia. But based on knowledge of specific genes that figure in other disorders (notably psychiatric disorders and other sleep disorders), scientists can guess which genes might be involved in insomnia and then conduct candidate gene studies on them. The aim of such studies is to compare variation in a gene suspected of causing insomnia in people with and without insomnia.

One gene that figures in the transport of serotonin (5-HTTLPR) has been studied for its relevance to depression and to insomnia. Huang and colleagues found that variation in this gene

  • significantly affected people’s vulnerability to insomnia, and
  • significantly predicted people’s reactivity to job-related stress.

Other candidate genes have been studied, including some that increase the risk of insomnia and others that protect against it. But few genes have been studied in detail and replication studies are still lacking.

Genome Wide Association Studies (GWAS)

GWAS allow scientists to examine millions of variants across the genome at the same time. Only four GWAS of genes potentially involved in insomnia have been conducted so far. But now that genotyping has become less expensive and management of data is easier, GWAS are the wave of the future.

One GWAS of interest was conducted by Australian researchers looking at insomnia and several aspects of sleep in a sample of twins. They found no genome-wide variants of significance.

But the most prominent finding was that a variant of CACNA1C, a gene associated with bipolar disorder, was also associated with sleep quality and sleep latency (the amount of time it takes to fall asleep). The relationship between CACNA1C and sleep quality was later replicated in a British study, suggesting that this gene may indeed be involved in insomnia.

CACNA1C codes for a mechanism that excites neurons and leads to the release of neurotransmitters. If this excitation occurs in neurons that promote wakefulness or neurons that inhibit sleep, this could lead to hyperarousal and trouble sleeping, in turn increasing a person’s risk of developing insomnia.

Why This Is Important

There hasn’t been much discussion of the factors that predispose us to insomnia—at least not in the popular press—and this is partly because not a lot is known about them. And at present little can be done to alter genetic traits.

But knowledge of the genetic underpinnings of insomnia will be increasingly important to the prevention and treatment of insomnia in the future. It could enable doctors to know which insomniacs will likely respond to treatment with cognitive behavioral therapy and which ones will not, or which medications will likely be effective and which will not.

Early intervention and prevention may also be possible once the risk and protective genes for insomnia are known. Further down the line, it may be possible to alter the expression of risk genes (with drugs that target gene regulation) or use gene therapy to replace defective genes.

All this may not help us manage insomnia now. But it’s heartening to know that scientists are pursuing knowledge that could take some of the guesswork out of treatment for insomnia and eventually render the treatments available today—imperfect as they all are—obsolete.

Comments, anyone?

Sleep Problems Following a Stressful Childhood

Only a minority of the insomnia sufferers I interviewed for The Savvy Insomniac said their insomnia began in childhood. But regardless of when their sleep problem began, a number reported having had stressful and/or abusive experiences in childhood.

Is there a relationship between adverse childhood experiences and insomnia later in life? Anecdotal and scientific evidence suggests there is.

insomnia can occur following a stressful childhoodOnly a minority of the insomnia sufferers I interviewed for The Savvy Insomniac said their insomnia began in childhood. But regardless of when their sleep problem began, a number reported having had stressful and/or abusive experiences in childhood.

Is there a relationship between adverse childhood experiences and insomnia later in life? Anecdotal and scientific evidence suggests there is.

Difficult Childhoods

Liz’s insomnia started in adulthood, worsening around the time of menopause. But she remembered being “a very, very nervous, anxious child”:

I have my suspicions that my trouble sleeping goes back a long, long way. My mother and father had difficulties and they fought a lot, and that made me anxious. I don’t think I feared for myself so much as I felt a general anxiousness about the disruption. Then I had a brother who was 6 years older than me and was always getting into trouble. He grew up with his father away in Egypt during the war. All of sudden he was 6 years old and he had a father and there were major problems between them. That was another disruption, another source of anxiety for me.

Keith thought it was the pattern of abuse he experienced at the hands of a family member that set him up for trouble sleeping:

I experienced severe childhood abuse—physical, emotional, and sexual abuse. It started when I was young and continued a long, long time. It happened early in the morning. When I wake up early now, and I often do, there’s frustration that I’m not able to sleep because I’m vigilant, I’m unable to relax. I’m pretty sure the childhood abuse is the source of my sleep difficulties.

What the Research Shows

Adverse childhood experiences (ACEs) increase people’s susceptibility to health problems later in life. The relationship between ACEs and mental illness, substance abuse, and heart disease is well documented. A recent literature review conducted by Harvard researchers shows that children who experience trauma are also more vulnerable to sleep disorders as adults.

In a majority of studies documenting this relationship, sleep problems were assessed subjectively, by the patients or participants themselves:

  • In a retrospective study of data collected from 17,337 HMO members, trouble falling and staying asleep was significantly associated with several types of childhood trauma: (1) physical abuse, (2) sexual abuse, (3) emotional abuse, (4) witnessing domestic violence, (5) household substance abuse, (6) household mental illness, (7)parental separation or divorce, and (8) household member imprisonment.
  • In a subsequent study, the authors found these same ACEs to be associated with frequent insufficient sleep.
  • In a longitudinal study, children who experienced family conflict between the ages of 7 and 15 were more likely to report insomnia at age 18.
  • Among women overall, there was a strong association between childhood sexual abuse and sleep disturbances reported in adulthood.

In two studies, sleep problems were assessed objectively using a wristwatch-type device:

  • Among 39 insomnia patients, a history of abuse and neglect explained a moderate amount of variance in sleep onset latency (39%), sleep efficiency (37%), number of body movements (40%) and moving time in bed (36%).
  • Among 48 psychiatric outpatients, childhood stress load was a correlate of total sleep time, sleep latency, sleep efficiency, and number of body movements.

Finally, the more traumatic childhood events people reported, the poorer was their quality of sleep:

  • People who experienced 1 to 2 ACEs were twice as likely to report poor sleep quality as people with no ACEs. People who experienced 3 to 6 ACEs were 3.5 times as likely to experience poor quality sleep as people with no ACEs.
  • As the number of ACEs went up, so did the prevalence of insufficient sleep.

Clearly adverse childhood experiences make it more likely that people will develop chronic insomnia or insomnia symptoms in adulthood. I did not experience familial abuse or neglect. I’m guessing, though, that the bullying I experienced one year at school increased my susceptibility to insomnia . . . but that’s a topic for another blog post.

How about you? Do you think there’s a link between your trouble sleeping and adversity you experienced in your youth?

Sleep Studies: Do You Really Need One?

If you haven’t had a sleep study, you may wonder if spending the night at a sleep clinic might help the doctor understand your problem and how to fix it. Polysomnography, or PSG, is the test conducted at the clinic. New guidelines from the American Board of Internal Medicine (ABIM) clarify when PSG is useful in cases of chronic insomnia and when it isn’t. Here’s a summary and explanation of the guidelines.

Sleep studies are useful when insomnia is complicated by another disorderWhen I ask people with persistent insomnia if they’ve had a sleep study, the common responses I get are these:

  • “I had one and all I learned from it was that I don’t have sleep apnea.”
  • “I want one, but my doctor won’t write the prescription.”

If you haven’t had a sleep study, you may wonder if spending the night at a sleep clinic might help the doctor understand your problem and how to fix it. Polysomnography, or PSG, is the test conducted at the clinic. New guidelines from the American Board of Internal Medicine (ABIM) clarify when PSG is useful in cases of chronic insomnia and when it isn’t. Here’s a summary and explanation of the guidelines.

When a Sleep Study Is in Order

PSG is good at detecting sleep apnea, sleep-related movement disorders, and violent or harmful behavior that might be occurring at night. If a doctor suspects that your insomnia is associated with any of these disorders, you’ll likely be going in for a sleep study.

Occasionally a person with insomnia reports such an unusual assortment of symptoms that, even after taking an extensive patient history, the doctor can’t figure out what’s going on. Here, too, PSG may help. The doctor may also prescribe a sleep study if you’ve undergone treatment for insomnia (with or without drugs) but your sleep has failed to improve.

When Sleep Studies Won’t Help

But neither the ABIM nor the American Academy of Sleep Medicine recommends sleep studies for other insomnia patients. Here are some of the reasons.

1.  PSG cannot do much except confirm the symptoms you report to the doctor during a clinical interview.

  • Let’s say you wake up several times at night and have trouble falling back to sleep. PSG may confirm that you experience these wake-ups but will not shed light on why.
  • Or maybe your problem is that it usually takes you a long time to fall asleep. Upwards of $2,000 is a lot to spend on a procedure that merely corroborates what you already know.

2.  PSG does a poor job of discriminating between normal sleepers and people with insomnia. In fact, up to 50 percent of the time, the brain activity of insomniacs looks identical to that of normal sleepers.

3.  In some insomniacs, there is abnormal brain activity occurring at night—activity typically associated with being awake. But standard PSG will not show evidence of this wake-like activity. As a measure of what’s going on in the brain at night, PSG is not finely tuned.

4.  Finally and importantly, in most cases of persistent insomnia, PSG will not suggest a course of treatment that differs from treatment that would be prescribed based on a thorough clinical interview.

  • If your complaint is that you’re a light sleeper and wake up frequently at night, the doctor will probably prescribe cognitive-behavioral therapy for insomnia (CBT-I) or some other behavioral treatment before considering medication. PSG might corroborate your symptoms but would not alter the diagnosis or the treatment.
  • Or let’s say your main complaint is that your thoughts keep you too wound up at night to fall asleep easily. The doctor isn’t going to need for you to undergo a sleep study in order to diagnose and treat the problem.

The Bottom Line

Sleep studies are an indispensable tool for people suspected of having sleep apnea and many other sleep disorders. But as conducted now, they’re of no help to insomnia sufferers unless your insomnia is related to another health problem.

If you’ve had a sleep study, what did you learn from it?