How to Become Smarter (21 page)

Most of these effects are temporary and disappear after you stop the cooling procedure. But the effect on alertness persists for several hours after the cooling, in my experience. There are some differences between cooling and psychostimulant drugs. Brief cooling does not change appetite, whereas many psychostimulants suppress appetite. There are no data in literature showing that cooling can cause addiction and psychotic symptoms. But psychostimulants can have these side effects when people use them without prescription and without a physician’s supervision. There are also differences in the effects that these treatments have on the brain.
^O
Evidence exists to support the beneficial effects of moderate cooling on alertness, fatigue, and mood.

A
LERTNESS
.
Several studies demonstrate a wakefulness-promoting effect. In one experiment [
343
] researchers placed rats in a cool environment, at an air temperature of 18°C (64°F), for four weeks. Researchers measured their total sleep time compared to control rats who lived at 24°C (75°F). The total time the cooled rats spent sleeping decreased by one-third during the first two weeks of the experiment. The sleep time returned to normal by the end of the third week [
343
]. Although this study did not measure activity, other studies report that rats exhibit increased activity when placed in a cold environment [
368
]. These data suggest that cooling has a psychostimulant effect. In another experiment, eight patients with multiple sclerosis tested the effects of a special cooling suit on their quality of life. Among other improvements, all eight patients reported increased alertness [
361
]. In another study, a group of Canadian researchers investigated the effects of both moderate and significant cooling on various mental abilities of healthy test subjects [
362
]. The
moderate
cooling consisted of immersion in cold water at 8°C (46°F) up to the neck for a few minutes. Under these conditions, core body temperature does not change significantly, but skin temperature drops. The scientists achieved the
significant
cooling by extending the immersion period to 55-80 minutes. In this case, core body temperature dropped below 35°C (95°F), which is a medical condition known as hypothermia. The healthy test subjects reported increased alertness with moderate cooling, but not with hypothermia. Furthermore, moderate cooling did not affect performance of simple mental tasks, but did improve performance of complex mental tasks compared to the control condition (no treatment) [
362
]. Hypothermia worsened performance of complex mental tasks.

Scientists in the Netherlands have reported that mild continuous cooling of the hands and feet by about 0.5°C (1°F) can reduce sleepiness in patients with narcolepsy [
379
]. Narcolepsy is a sleep disorder characterized by excessive daytime sleepiness. In that experiment, such cooling of the largest area of the skin excluding the head, hands, and feet, was not effective at reducing abnormal sleepiness in the patients. A slight
increase
of core body temperature of the narcoleptic patients by means of hot food and drinks was effective at improving vigilance during repetitive tasks [
379
]. In the rats living in a cool environment in the above experiment, core body and brain temperature increased slightly [
343
]. Cold showers and immersion in cold water at 20°C can also increase core body temperature [
378
] by about 0.1 to 0.2°C (0.2 to 0.4°F), when the body temperature is normal. Wakefulness-promoting drugs also tend to cause a small increase in core body temperature [
332
]. To summarize these studies, surface cooling of the body can increase wakefulness. (
Endnote P
describes possible physiological mechanisms.)

F
ATIGUE
.
Some of the first studies of the effects of body cooling on fatigue appeared in the 1960s [
363
,
364
]. One showed that exposure to cold air can reduce mental fatigue in children with or without physical exercise [
363
]. Another study, which investigated the effects of abdominal cold packs and cold showers on adults, concluded that these interventions can reduce fatigue [
364
]. A series of more recent studies, which included both healthy subjects and patients, revisited the effects of cooling on fatigue [
361
,
365
,
366
]. The observation that in some disorders (for example, multiple sclerosis) fatigue can increase in a warm environment [
367
] served as an impetus for some of these studies. These data led to the development of a cooling suit [
380
]. Two studies using a small number of multiple sclerosis patients (8 and 10 participants) showed that the cooling suit can reduce fatigue both in a warm and in a thermoneutral environment [
361
,
380
]. The authors concluded that this treatment can improve quality of life of multiple sclerosis patients [
361
]. Several other studies investigated physiological effects of winter swimming, a practice widespread in Finland [
365
,
374
,
375
]. Winter swimming involves immersion in ice-cold water, 1-10°C (34 to 50°F), for several minutes. After participants in two Finnish studies reported reduced tiredness [
374
,
375
], the authors set out to investigate the effects of winter swimming on general well-being, including fatigue [
365
]. In that report a mixed group of volunteers, which consisted of healthy subjects and some patients with physical illnesses, used winter swimming 4 times a week for a total of 4 months. The study showed that winter swimming caused a significant reduction of fatigue compared to the control group (no treatment) [
365
]. The winter swimming group included patients with fibromyalgia and rheumatoid arthritis, disorders often associated with chronic fatigue. Although this study did not report adverse effects of winter swimming among participants, you need to be extremely careful with this procedure. It can cause hypothermia and its associated adverse effects on health (detailed in the section “Potential adverse effects” below).

Interestingly, several reports show that body cooling during exercise or between exercise bouts can improve athletic performance [
366
,
381
-
383
]. Moderate cooling of the body shares a number of biological effects with psychostimulant drugs. Therefore, it is no surprise that moderate cooling reduces fatigue because most psychostimulants do. (
Endnote R
discusses possible physiological mechanisms.)

M
OOD
.
Some stimulants elevate mood in healthy people and this is also the case with moderate cooling. Several studies have demonstrated that brief cooling of the body improves mood in healthy people and in some groups of patients [
365
,
371
-
376
]. A study in 1983 showed that swimming in a pool can improve mood [
371
]. The temperature of water in a public swimming pool (27 to 29°C or 81 to 84°F [
384
]) is lower than normal body temperature. Thus, the modest cooling effect may have been responsible for the improvement of mood in swimmers. The authors concluded that the physical exercise associated with swimming (50 minutes per session) is responsible for the mood change [
371
]. A recent clinical trial in Iran showed that swimming in a pool has a weak-to-moderate antidepressant effect [
385
]. Several studies of winter swimmers [
365
] support this finding. Winter swimming does not involve significant amounts of physical exercise. It does, however, involve substantial cooling of the body because immersion in water colder than 16°C (61°F) can cause hypothermia (core body temperature of 35°C {95°F} or lower) in human subjects [
386
]. Two initial studies of winter swimmers in Finland focused on physiological changes caused by this practice and participants often reported improvement of mood and self-esteem after immersion in cold water [
374
,
375
]. These observations prompted the authors to investigate the effects of winter swimming on mood. Their study showed that the participants’ scores on the “Profile of Mood States” questionnaire improved after four months of winter swimming four times a week [
365
]. The participants consisted of healthy subjects and some patients with physical illnesses (asthma, rheumatoid arthritis, osteoarthritis, hypertension, hypothyroidism, Parkinson’s disease, and fibromyalgia) and did not include patients diagnosed with depression [
365
]. Another study investigated the effect of a cooling suit on fatigue and quality of life in multiple sclerosis patients. The authors reported that 5 patients out of 8 experienced “feelings of well-being and happiness” after cooling and the other 3 participants had less irritation caused by fatigue [
361
]. A study at the National Institute of Mental Health investigated the effects of environmental temperature on the symptoms of several patients with summer seasonal depression [
387
]. These patients developed symptoms of depression every summer. One female patient, who tested cold showers several times a day during the summer, showed a dramatic improvement of depressive symptoms after 5 days of this regimen. After that, she discontinued cold showers for 9 days and had a complete relapse of depression [
387
].

To date there have been no statistically significant trials of cold-water treatments as a single therapy for depression. Nonetheless, a recent research paper out of Poland showed that the addition of cryotherapy to pharmacological treatments reduced depressive symptoms in a group of 26 patients with depressive and anxiety disorders [
376
]. Cryotherapy is brief cooling of the body by means of extremely cold air (minus 110-160°C or minus 170-250°F) in a special chamber [
376
]. Originally, researchers developed it for the treatment of rheumatoid arthritis: cryotherapy reduces pain and inflammation in this disorder [
376
,
388
]. A group of Polish researchers observed in the late 1990s that, after several minutes in a cryogenic chamber, in addition to having less pain, patients often experienced improved mood and euphoria [
373
]. This observation led the group to hypothesize that cryotherapy has antidepressant properties and resulted in the above study of cryotherapy as an adjunctive (supplementary) treatment of depression [
376
].

Some of the above studies reported that body cooling can elevate normal mood. This is a euphoriant effect and it is not the same as the antidepressant effect, which means normalization of depressed mood. Most antidepressant drugs do not have euphoriant properties [
8
,
389
]. On the other hand, psychostimulant drugs that have euphoriant properties are not effective or are marginally effective as antidepressants [
390
]. The one notable exception is a drug called tianeptine (brand names
Coaxil
®,
Stablon
®), which has both euphoriant and antidepressant effects [
391
,
392
]. The FDA has not yet approved this drug as a treatment for depression in the United States, although government regulators approved it a long time ago in many non-English-speaking countries.

In summary, these studies suggest that brief cooling of the body improves mood in healthy people and that the addition of this treatment to pharmacotherapy benefits patients diagnosed with depression. Further clinical studies are warranted because, in addition to the above data, theoretical evidence
^S
suggests that this approach shares some physiological mechanisms with existing antidepressant treatments. Therefore, cooling may be effective as a stand-alone treatment for depression [
372
,
376
]. Cooling of the body lowers the level of serotonin in the brain [
679
,
680
], which is the mode of action of the above-mentioned drug tianeptine. Cooling also can increase the level of the chemicals dopamine and norepinephrine in some regions of the brain [
472
,
659
,
686
,
687
]. This is similar
^S
to the mode of action of another antidepressant drug, bupropion (brand name
Wellbutrin
®). Since many classes of antidepressant drugs exhibit antianxiety properties, it is possible that moderate repeated cooling such as adapted cold showers (described later) may also be beneficial in some anxiety disorders.
^S
The aforementioned Polish study showed that cryotherapy is beneficial for patients with anxiety. In my own experience, combining the cooling treatments with the “antidepressant diet” (Chapter Four) is more effective against symptoms of depression and anxiety than water therapy alone.