How to Become Smarter (67 page)

Readers can find a more detailed discussion of this topic elsewhere [
577
]. Practical aspects of applying hyperthermia as a tranquilizing treatment warrant some elaboration. Hyperthermia does not have to be maintained constantly and a temporary hyperthermia that is repeated daily (let’s say, 30 minutes per day) may be effective. A convenient way to increase core body temperature is a hot bath or immersion in hot water up to the neck. I am a healthy subject and have never had a diagnosis of a psychotic disorder; therefore, I cannot say if repeated hyperthermia is an effective neuroleptic treatment. It does however induce disabling fatigue if core body temperature reaches 39°C. This treatment helps to calm down in the context of the experimental model of hypomania from
Chapter Four
, although the sedation lasts only several hours and subsequently there is a swing in the opposite direction. If sedation is necessary, a continuously hot environment (29-30°C) is more effective. In this case, the core body temperature needs to be monitored at certain intervals to prevent heat-related illnesses, such as heat exhaustion or heat stroke [
654
]. Hyperthermia is not effective as a sleeping aid, whereas moderate heating, such as a hot shower or hot environment that will not affect core body temperature, is beneficial as a sleeping aid, an observation that is consistent with some studies [
349
,
350
].

One possible problem with hot baths is that if the temperature is relatively high (42-43°C), then this treatment can inhibit the function of T lymphocytes [
656
,
657
]; that is, it may negatively affect the immune system (blood carrying T lymphocytes passes through the overheated epidermis). I used this sort of hot baths on a daily basis in two separate experiments in the early 2009. I took the hot baths in the evening, daily. The bath lasted for 20-30 minutes until core body temperature reached 39°C. In both cases, I developed a respiratory infection after 10 to 14 days of this protocol and had to abort the experiment. Other undesirable effects that I observed after hyperthermic treatments are dry mouth and bad breath.

Another potential problem is skin irritation and itching, especially feet and shins. To sum up, the high temperature of water can induce hyperthermia relatively quickly (within 30 minutes), but may cause immunosuppression and skin irritation if a person uses this procedure on a daily basis. Thus, a slower protocol may be safer. For example, one can set water temperature to 39.5°C and vigorous (automatic) stirring of water may accelerate body heating. I have not tested this approach.
Endnote F
describes another approach to nonpharmacological inhibition of cerebral dopaminergic activity.

(L
AY
L
ANGUAGE
S
UMMARY
): Body cooling and psychostimulant drugs have somewhat different effects on the brain. For instance, cooling increases the synthesis of dopamine by neurons, whereas stimulants merely shift existing dopamine from the inside to the outside of neurons. Amphetamine increases dopamine activity in the frontal part of the brain, which is crucial for attention control. This is not the case for cooling.

In the main text, we talked about an experiment on rats which showed that exposure to cold can increase the synthesis of dopamine in the striatum by about 50%, but has no effect on dopamine metabolism in the frontal cortex [
472
]. Cooling and dopaminergic drugs have different effects on the striatum because dopamine reuptake inhibitors shift intracellular dopamine to the extracellular space, which can cause subsequent depletion of intracellular dopamine stores (at high doses of the drugs) [
658
]. On the other hand, exposure to cold increases the synthesis of dopamine [
472
], which will not result in dopamine depletion. One can usually interpret increased synthesis of dopamine as an elevated discharge rate of the dopaminergic neurons projecting to the brain region in question [
329
]. Another difference is that exposure to cold is unlikely to cause a several-fold increase of extracellular dopamine in the striatum (the increase in dopamine synthesis is about 50%), whereas sufficiently high doses of cocaine or amphetamine can increase the concentration of extracellular dopamine by 5-fold or greater [
331
]. Finally, because cooling does not affect dopamine metabolism in the frontal cortex [
472
], this treatment is unlikely to be beneficial in ADHD, since prefrontal cortex is the main regulator of attention function [
294
,
628
].

Mechanisms underlying the wakefulness-promoting effect of cooling
(L
AY
L
ANGUAGE
S
UMMARY
): Similar to psychostimulants, moderate cooling of the body enhances the activity of the brain region responsible for wakefulness. Some types of cooling are less effective than others. This section also contains a table comparing various biological effects of cooling and heating.

Literature suggests that moderate surface cooling has several physiological effects that resemble those of psychostimulant agents. For example, both types of treatment can increase locomotor activity of laboratory animals [
368
-
370
]; can stimulate components of the reticular activating system, such as locus ceruleus [
332
,
370
,
659
-
664
]; can enhance dopaminergic activity in the striatum [
472
,
658
], can reduce the plasma level of prolactin [
665
-
670
], and can stimulate thermogenesis [
332
,
343
,
378
]. Since psychostimulants tend to promote wakefulness and disrupt sleep, moderate cooling should have a similar wakefulness-promoting effect. There are a number of different ways of cooling the body and each of them will have different physiological effects. For example, a research team in the Netherlands showed that cooling of the hands and feet can promote wakefulness [
379
], whereas lowering of core body temperature (by ingestion of cold food and drinks) has the opposite effect, namely, it promotes sleep [
351
]. Cooling procedures that do not lead to hypothermia tend to have an alerting effect [
332
,
343
,
361
,
362
], whereas moderate and severe hypothermia can cause mental confusion and psychomotor retardation [
419
,
420
]. Put another way, methodological details are important for obtaining the desired wakefulness-promoting effect of cooling. The known effects of cooling and heating of the body are summarized in
Table 8
below. For some effects (labeled with an asterisk in the table), the level of evidence is weak.

Table 8.
Comparison of short-term physiological effects (0.5 to 3 hours) of cold and hot hydrotherapy.

----------------------------------

Immediate effects on mood

Heating (that causes hyperthermia)
:
depresses normal mood, but may improve depressed mood*

Cold hydrotherapy (without hypothermia)
:
can lift depressed* and normal mood

Fatigue

Heating (that causes hyperthermia)
:
increases

Cold hydrotherapy (without hypothermia)
:
reduces

Cognitive performance

Heating (that causes hyperthermia)
:
worsens

Cold hydrotherapy (without hypothermia)
:
may improve slightly*

Psychomotor agitation*

Heating (that causes hyperthermia)
:
reduces

Cold hydrotherapy (without hypothermia)
:
may enhance

Sleep

Heating (that causes hyperthermia)
:
disrupts or no effect (moderate heating without hyperthermia promotes sleep)

Cold hydrotherapy (without hypothermia)
:
disrupts

Plasma epinephrine

Heating (that causes hyperthermia)
:
increases

Cold hydrotherapy (without hypothermia)
:
no change

Plasma norepinephrine

Heating (that causes hyperthermia)
:
increases slightly

Cold hydrotherapy (without hypothermia)
:
increases over 4-fold

Plasma serotonin

Heating (that causes hyperthermia)
:
increases

Cold hydrotherapy (without hypothermia)
:
no change

Total brain serotonin

Heating (that causes hyperthermia)
:
increases

Cold hydrotherapy (without hypothermia)
:
reduces

Plasma prolactin

Heating (that causes hyperthermia)
:
increases

Cold hydrotherapy (without hypothermia)
:
reduces

Plasma adrenocorticotropic hormone

Heating (that causes hyperthermia)
:
increases

Cold hydrotherapy (without hypothermia)
:
increases

Plasma cortisol

Heating (that causes hyperthermia)
:
increases

Cold hydrotherapy (without hypothermia)
:
reports are inconsistent

Plasma beta-endorphin

Heating (that causes hyperthermia)
:
increases

Cold hydrotherapy (without hypothermia)
:
increases

Physical pain

Heating (that causes hyperthermia)
:
reduces (but may provoke headache in some patients)

Cold hydrotherapy (without hypothermia)
:
reduces

Effect on inflammatory conditions

Heating (that causes hyperthermia)
:
may aggravate

Cold hydrotherapy (without hypothermia)
:
improves

Effect on peripheral vasculature

Heating (that causes hyperthermia)
:
vasodilatation

Cold hydrotherapy (without hypothermia)
:
vasoconstriction

Blood pressure

Heating (that causes hyperthermia)
:
reduces elevated blood pressure, no change in normal blood pressure

Cold hydrotherapy (without hypothermia)
:
cold shower increases whereas immersion in cold water at 20°C reduces blood pressure (due to diving reflex)