Insomnia: when our brain refuses to let us rest

An import­ant early morn­ing appoint­ment can be enough to make it dif­fi­cult to fall asleep. Is it out of fear of not wak­ing up in time? It leads to wor­ry­ing, brain activ­ity and hyper­vi­gil­ance that are often incom­pat­ible with fall­ing asleep. This example, one that is surely famil­i­ar to a lot of people, neatly sum­mar­ises some of the things that can cause insom­nia, and why our brains some­times refuse to let us rest. If this situ­ation sounds famil­i­ar to you, it only reflects the more occa­sion­al side of the dis­order. Chron­ic insom­nia, on the oth­er hand, is the res­ult of deep­er and more com­plex mech­an­isms, which can cause this dis­order to become long-term. A dis­order which, moreover, is much more about hyper-arous­al than sleep.

Accord­ing to stud­ies, chron­ic insom­nia affects between 15 and 20%¹ of the French pop­u­la­tion. This con­di­tion, which affects women (20%) more than men (10%), is still not well under­stood. Pierre-Alex­is Geof­froy, pro­fess­or at the Uni­ver­sity of Par­is-Cité and head of the Chro­noS Centre (Psy­chi­atry, Chro­n­o­bi­o­logy and Sleep) of the GHU Par­is psy­chi­atry & neur­os­ciences, tries to explain it with the 3P factors mod­el (pre­dis­pos­ing, pre­cip­it­at­ing, per­petu­at­ing²): “We know that there is a genet­ic vul­ner­ab­il­ity. The her­it­ab­il­ity, and there­fore the part of the dis­ease linked to genes, is still decis­ive at 40%, which is equi­val­ent to type 2 dia­betes. In this risk area [Editor’s note: cor­res­pond­ing to the pre­dis­pos­ing factor], pre­cip­it­a­tion can occur, linked to trauma, infec­tion, depres­sion or oth­er forms of stress, both phys­ic­al and psy­cho­lo­gic­al. The con­di­tion then has a chance to take hold, with per­petu­at­ing factors such as anxi­ety, and dys­func­tion­al emo­tions and beha­viours related to sleep.”

We are there­fore deal­ing with an atyp­ic­al dis­order. First, it is not just a symp­tom of oth­er con­di­tions, but a dis­order in its own right, often with comor­bid­it­ies. Secondly, it is fuelled by sev­er­al factors, both bio­lo­gic­al and psy­cho­lo­gic­al, which feed into each oth­er. It is a kind of vicious circle which, once we are caught up in it, can only get worse.

To under­stand how we become insom­ni­acs, it is inter­est­ing to delve into the cereb­ral mech­an­isms at the root of this hyper­arous­al dis­order. When it comes down to it, for our brain, sleep­ing almost means flick­ing the switch. This mech­an­ism is also rep­res­en­ted by means of a sys­tem known as the “flip-flop³”, like a seesaw, groups of neur­ons inter­act with each oth­er to either activ­ate or inhib­it each oth­er. On one side of the seesaw, we can say that we are in wake­ful­ness mode, on the oth­er in sleep mode. 

“Our brain has a wake­ful­ness sys­tem, called the ascend­ing retic­u­lar activ­at­ing sys­tem (ARAS),” explains Pro­fess­or Geof­froy “This includes all monoam­in­er­gic struc­tures, i.e. neur­o­trans­mit­ters such as histam­ine, sero­ton­in, dopam­ine, norad­ren­aline, etc. Then comes the ventro­lat­er­al pre­optic nuc­le­us (VLPO), which is present to inhib­it these arous­al struc­tures; these are GABAer­gic activ­it­ies [Editor’s note : the neur­ons release gamma-aminobu­tyr­ic acid (GABA), the brain’s main inhib­it­or].” In short: when awake, the ARAS is act­ive and when asleep, the VLPO inhib­its this activ­ity. The switchover is gradu­al and, syn­chron­ised with our cir­ca­di­an rhythms, it is the orex­in that sta­bil­ises the whole pro­cess. “A defi­ciency of this molecule (orex­in) induces a dis­ease called nar­co­lepsy, caus­ing cent­ral hyper­som­nia with unwanted excess sleep,” he adds. One of the new treat­ments for insom­nia aims to tar­get orex­in to reduce this state of alertness.”

But how does this sys­tem fail when it comes to insom­nia? This fol­lows the logic of the 3Ps men­tioned above: “Vul­ner­ab­il­ity, also known as pre­dis­pos­i­tion, is cer­tainly genet­ic, but it is also in con­stant inter­ac­tion with the envir­on­ment,” explains Pierre-Alex­is Geof­froy. “The bed, the room, the noise, all factors that can com­plic­ate or simply impair the qual­ity of sleep. Then there are pre­cip­it­at­ing factors that push the brain into hyper­vi­gil­ance, pre­vent­ing it from trig­ger­ing the VLPO, which is sup­posed to inhib­it our state of wake­ful­ness.” Stress, for example, through cortisol, its main hor­mone, delays fall­ing asleep. At the same time, cer­tain emo­tion­al cir­cuits, such as those of the amy­g­dala or the pre­front­al cor­tex, will main­tain a state of increased alert­ness. “Dys­func­tion­al beha­viour, due to the dis­com­fort of insom­nia, then appears,” he observes. “The patient starts count­ing how many hours of sleep they get, or their inab­il­ity to fall asleep causes even more stress. From there, the ill­ness becomes per­man­ent, it settles in and becomes chronic.”

Of course, chron­ic insom­nia is still strictly dia­gnosed. Accord­ing to the DSM‑5, an insom­ni­ac is any patient exper­i­en­cing these dif­fi­culties at least 3 nights a week, for at least 3 months. It must also have a debil­it­at­ing impact on the patient’s daily activ­it­ies. This explains why, even though 50% of French people com­plain of insom­nia, only 15% meet the cri­ter­ia for a dis­order or ill­ness. Accord­ing to Pierre-Alex­is Geof­froy, this dif­fer­ence in pre­val­ence may also be due to under­dia­gnos­is: “We have pub­lished an inter­est­ing art­icle⁵ that puts into per­spect­ive the cul­tur­al dif­fer­ences in the way sleep is per­ceived. In Ger­many, for example, patients tend to see a spe­cial­ist very quickly – 20% will see a sleep spe­cial­ist and 17% a psy­chi­at­rist. In France, it’s the oth­er way around and the fig­ures are alarm­ing, because almost all people who identi­fy a poten­tial sleep prob­lem will not go and seek advice from specialists.”

How­ever, there are treat­ments avail­able to break this vicious circle, with cog­nit­ive beha­vi­our­al ther­apy for insom­nia (CBTI) being the pre­ferred option. “Sleep is very much a beha­vi­our­al thing. There are con­di­tion­ing factors, in addi­tion to cir­ca­di­an rhythms, that encour­age sleep. The bed, for example, becomes a real battle­ground in insom­nia,” Pro­fess­or Geof­froy explains. “Fur­ther­more, we need to under­stand the ori­gin of the dis­order. If it is caused by depres­sion, the depres­sion will need to be treated first. How­ever, if it is not recog­nised as a dis­order in its own right, rather than as a simple symp­tom, the dis­order can per­sist even once the depres­sion has been addressed.” A prime example is the impact of dis­rup­ted nights due to post-preg­nancy situ­ations. Des­pite nev­er hav­ing exper­i­enced any dif­fi­culty in sleep­ing, many women testi­fy that, after preg­nancy, their sleep habits are turned upside down. In these situ­ations, par­ents are always on the alert, which clearly implies a state of hyper­vi­gil­ance. A num­ber of women still suf­fer from insom­nia after this period.

There is still a lot of con­fu­sion in the treat­ment of insom­nia, redu­cing CBTI to simple sleep hygiene. “CBTI is a mul­ticom­pon­ent ther­apy,” he adds. “Sleep hygiene is fun­da­ment­al, but there is also cog­nit­ive restruc­tur­ing to work on dys­func­tion­al thoughts. Work on beha­viour is also neces­sary, such as restrict­ing the time spent in bed or stim­u­lus con­trol. This treat­ment works very well and will inhib­it the arous­al struc­tures involved in insomnia.”

It is there­fore pos­sible to over­come this dis­order, which greatly han­di­caps the daily life of the patient affected. Pierre-Alex­is Geof­froy emphas­ises: “It is a dis­order in its own right, and not just a night-time dis­order, but a 24-hour one! We tend to under­es­tim­ate the import­ance of sleep when we sleep well.” A recent study⁶ also shows that sleep dis­orders are the main pre­dict­or of psy­chi­at­ric disorders.

Pablo Andres