BIOLOGICAL RHYTHMS: WHAT ARE THEY AND HOW DO THEY WORK? - NEUROPSYCHOLOGY - 2025

The biological rhythms are fluctuations in physiological variables within a time interval. They have traditionally been studied from disciplines such as Biology, since biological rhythms are present in both plants and animals, or from Medicine; however, more and more research in Psychology addresses this issue.

Something as simple and everyday as eating three times a day, getting up more or less always at the same time or being more active at a certain time of the day responds to a very complex network of somatic interactions called biological rhythm.

Background on interest in biorhythms

The study of this phenomenon; that is to say, of the periodicity of many physiological aspects, it attracted the attention of doctors and philosophers of antiquity. Especially from Galen and Aristotle, who attributed biorhythms to the action of the environment: the subject is only susceptible to external factors (for example, the sunset to sleep) and is considered a passive agent of the environment.

It was not until the nineteenth century when all astronomical explanation was discarded and it began to be suggested that there are endogenous factors (see hormonal) that influence the biorhythms of living organisms. We will talk about hormonal factors later, but surely you have heard of the famous melatonin in sleeping pill format.

The issue of biorhythms had its heyday with those known as biorhythmists at the end of the 18th century and throughout the 19th century. As a curiosity, the Berlin doctor Wilhelm Fliess (who, by the way, was Freud's patient) observed that many patterns (including births and deaths) occur at intervals of 23 and 28 days.

He called male cycles those that occur every 23 days and female cycles that occur every 28 days, making it coincide with menstruation.

Later, at the University of Innsbruck it was observed that students' "lucky days" occurred every 33 days and came to associate it with a supposed cyclical learning capacity of the brain, which absorbed knowledge better every certain period of time.

Of course, all this has been relegated to an anecdotal level and today the subject of biorhythms is approached from a positivist perspective and from the assumptions of science, which will be what we will deal with in the following paragraphs.

We can, however, advance a more scientific view of this phenomenon: the one that supports that our brain function fulfills cycles of approximately 90 minutes, coinciding with what is known as paradoxical or REM sleep (for example, there is a decrease in concentration at 90 minutes of studying).

Types of biorhythms

Science has identified three different types of biorhythms: circadian, ultradian, and infradian.

Cardiac rhtyms

Etymologically, this word finds its Latin origin in circa- (around) and -dies (day), therefore we can deduce that circadian rhythms are those physiological oscillations that occur approximately every 24 hours.

A good example of this would be the need for sleep. Under normal conditions, sleep comes to us at practically the same time of day following a marked pattern. Any alteration of this pattern leads to disorders such as insomnia.

It is not surprising, by the way, that our "internal clock" is regulated by daylight and by a schedule and that if it is disrupted, disorders as annoying as jet lag appear, which is neither more nor less than an alteration of our circadian rhythm and further proof that we are regulated, in part, by the hours of light we have per day.

In addition to the aforementioned insomnia, in Psychopathology there are also alterations that make up circadian rhythms. For example, people with severe depression feel worse in the morning (morning worsening) and get better in the afternoon.

In fact, some of the first symptoms that patients with depression manifest are the so-called rhythm diseases, or disorders of biological rhythms, normally identified in clinical psychology as deficits of appetite, sexual desire and sleep.

Infraradian rhythms

They are those whose duration or cyclicality is greater than 24 hours. They are so called (infra- means minor in Latin) because they occur less than once a day. This, which can be complicated, is easier to see if we put examples of it.

Menstrual cycles illustrate this phenomenon well: they occur approximately every 28 days. The tides and lunar phases also correspond to infradian rhythms, also following a pattern of between 24 and 28 days.

That is why the menstrual period is sometimes referred to as a circalunar rhythm; However, the scientific evidence does not really give rise to consider it as such on a solid basis.

This is due to the fact that many factors of modern life (the use of curtains that do not allow light to pass through, finding ourselves working in an environment with artificial light, etc.) do not allow a synchrony of the woman's rhythms with the lunar cycle.

Another curious infradian phenomenon is the fact that some species of insects, such as lion ants, dig deeper and better wells and ant hills when there is a full moon (Goodenough, 1993)

Another good example could be the migration of birds or any similar phenomenon that occurs seasonally.

Applying it again to the field of psychopathology, depressions and other mood disorders tend to worsen in spring and sometimes in the early fall. Bipolarity is also associated with seasonal worsening.

Ultradian rhythms

They are those that take place in a period of time less than 24 hours; that is, they occur more than once a day (ultra- means greater in Latin). There are many ultradian rhythms, such as the heartbeat, the blinking of the eyes, the regulation of body temperature or breathing.

Other ultradian rhythms can be REM sleep cycles (which occur every 90 minutes or so) or foraging in animals.

Internal factors involved

Now that we have seen the importance of maintaining homeostasis or balance in our body, it is time to comment on the endogenous factors that are involved in the control of our internal clock.

To situate ourselves a little more, it is said that biorhythms are endogenous (they are controlled by internal signals from our body) but they are regulated by synchronizers, such as the hours of light that we mentioned above. Changes in light and dark keep our watch adjusted.

Melatonin

It is a hormone that is found in animals, plants and fungi and its fluctuations vary according to the time of day and the lighting of the moment. It is found mainly in the pineal gland, located in the suprachiasmatic nucleus of the brain, and exposed and identifiable to the eye in some reptiles (also called "the third eye" for that reason)

If we remove this nucleus under experimental conditions, we will observe that the animals do not show any circadian rhythm, showing numerous disorders, especially sleep-wakefulness.

Melatonin, which we can find without a prescription in any supermarket or parapharmacy, is being used in recent times as a treatment for insomnia and to replace benzodiazepines (drugs ending in -pam).

Cortisol

It is a steroid hormone (like testosterone) that is released especially in stressful situations and whose half-life in the body is approximately 90 minutes.

Prolonged exposure to stressful events causes the continued release of cortisol, leading to a high probability of rhythm disease.

Luteinizing Hormone (LH)

This hormone is responsible for ovulation, which takes place in the middle of the menstrual cycle approximately every 13-15 days. It follows a cyclical pattern and is key for menstruation to occur normally every 24-28 days.

Follicle-Stimulating Hormone (FSH)

In addition to being in synergy with LH in women's infradian cycles, FSH triggers maturation at puberty in both males and females, as well as development and growth. In men it is also involved in the production of sperm.

Circadian rhythm and routine

We have already seen the importance of cycles in our body and in that of other species. However, the current pace of life often prevents us from giving our body the biorhythm it needs to adjust both internally and externally.

It is also true that many people (ignoring those who have to work a night shift for work reasons) are more nocturnal than daytime; that is to say, they are more active at night, and surely we know someone whose performance studying is higher during the early morning.

This is certainly not harmful per se as long as we try to meet that schedule on a regular basis so as not to drive our body or internal clock "crazy". Let us remember that our body adjusts under normal conditions to circadian rhythms of approximately 24 hours of biological duration.

At this point, it is convenient to talk about how to maintain a daily routine that allows us to have an internal clock with a mechanism as refined as one made in Switzerland. Here are some tips that, if we follow them, we will surely notice an improvement in our vitality and performance.

• Always try to get up at the same time, if possible early: but be careful! we have to respect a few hours of sleep. This means that if, for whatever reasons, we have gone to bed at 3 in the morning, we do not force the machinery to be in the plant at 7. In the long run, this lack of sleep will affect us in all aspects. Of course, it doesn't hurt to also have a schedule to go to bed.
• Eat the most important meals of the day within the same time slot.
• Make it a goal to be more disciplined - for example, make a to-do list on a daily basis and don't move on to another activity until they're all done.
• When you are on an extended vacation, for example in summer, try not to neglect your usual routine during the rest of the year. This will help you sit up without feeling too out of place.
• Procrastinating has to be totally undesirable for you. It is difficult, but it will help your productivity and you will feel more satisfied and, probably, with much less anxiety about doing tasks. That is why it is essential to put the mobile aside and, if necessary, remove the Internet connection from our computer.
• Of course, willpower will be essential and, like almost everything, it can be trained and tested in even the most insignificant gestures: not getting up from your chair until you have finished studying a topic or it is time for dinner.
• Use a planner or calendar to keep track of your goals. Writing makes you more aware of your actions and allows you more accurate monitoring.
• It is advisable to use an activity as the starting point of the day. For example, if you like to play sports or have some goal related to improving your physical form (which, in fact, we all should do) you can consider that all your days start with a half-hour run at a moderate jog. It will help us activate.
• We will observe, as we establish a habit, that with the correct organization of our routine we will have more free time for leisure activities.
• Find a time of day (preferably at sunset or before bed) to meditate, stretch, or do some yoga. These "sleep hygiene" habits will help us sleep better and keep insomnia at bay.
• Remember that, on average, a habit takes 20 days to establish. From there, everything will go smoothly and it will not cost us so much effort or it will be so tedious to maintain a good daily routine.

Conclusions

The importance of maintaining a daily routine as part of a good synchronization of our biorhythms becomes especially relevant if what we want is to maintain both physical and mental health in an optimal state.

In addition to our body thanking us for it, at the self-realization level we will notice the results as soon as we notice that our productivity and efficiency are affected.

Finally, and as we said, discipline is essential in this journey that involves taking care of ourselves and respecting ourselves, where maintaining a healthy routine can be a good starting point.