For those dwelling in climates prone to the dark, chilly days of fall and winter, it is widely understood that along with changes in the natural world, seasonal shifts in mood and temperament are also likely to occur. These shifts may be more drastic and debilitating for some than for others, and when seasonally induced woes weigh too heavily on a person, he or she may be diagnosed with conditions like depression or seasonal affective disorder (SAD). While such diagnoses have become quite common, people are just recognizing consensus among researchers that a person’s season of birth appears to increase the chances that a person will develop these or other mental health conditions.
Typically, a person’s birthdate is given astrological significance in the form of a zodiac sign, but not necessarily predictive powers when it comes to psychological well-being. There was a time not so long ago when the study of astrology was considered to be of scholarly and scientific value in treating physical maladies, but few modern-day doctors still refer to the celestial bodies when determining diagnoses and treatment conditions (Wolfson, 2013). However, a connection between season of birth and certain mental health conditions has been observed by a number of researchers in recent years. The primary finding of this vein of research is that being born in the fall, winter, and spring increases the chances of mental and emotional instability.
The most widely researched correlation is the heightened likelihood of developing schizophrenia if a person is born in the darker, colder months of the year—winter, primarily. Over 200 studies have confirmed this correlation since 1929 (Wolfson, 2013), including one study which revealed that being born in the Northern Hemisphere in either winter or spring may increase the tendency toward schizophrenic symptoms (Davies, Welham, Chant, Fuller Torrey, and McGrath, 2003).
In this particular study, researchers compared winter/spring versus summer/autumn births using data from eight preexisting studies of 126,196 people who had been diagnosed with schizophrenia and 86,605,807 “general population births.” The subjects were located in 27 sites across the Northern Hemisphere, and the positive correlation between schizophrenia and winter/springtime birth as well as latitude-based weather conditions was reported as “small but significant” (Davies et al., 2003).
Further studies reveal that a similar connection exists between season of birth and SAD. Pjrek et al. (2004) discovered a notable link with being born in the fall and winter and experiencing “melancholic depression” during those times of year as an adult. This finding inspired additional research that explored and confirmed the apparent correlation of SAD and season of birth (Pjrek et al., 2007).
Yet another study conducted in England examined the correlation between season of birth and schizophrenia, bipolar, and recurrent depression in “the largest cohort of English patients collected to date” (Disanto et al., 2012). Once again, they found that those born during darker days and colder temperatures were more likely to develop these conditions later in life. Specifically, cases of schizophrenia and bipolar were found to be at their peak in those born in January, and at their lowest rate of occurrence in July, August, and September births. A slight deviation from the fall-winter-early spring correlation was their discovery that those born in May appeared to be particularly susceptible to recurrent episodes of depression.
Overall, the message seems to be that a large portion of the population is primed to experience what are commonly known as mood disorders from birth; ultimately, the only ones who are not at a high inborn risk of developing these conditions are those whose birthdays are in the sunshine-rich summer months. This has led some researchers in England to theorize that vitamin D deficiency—whether in the biological mother or in the child after birth—factors in to these findings (Disanto et al., 2012). So the explanation for this phenomenon could be as simple as less exposure to sunlight depriving a person of sunnier brain chemistry from birth. These same researchers also posit that environmental exposure to viral or bacterial strains on the part of the mother during these times of year may play a part in their children’s psychological development.
Another widely held theory, shared by neuroscientist Chris Ciarleglio in a recent article published in The Atlantic, suggests that “developing in a certain season seems to imprint your circadian clock,” which is known to have a strong influence on mental and emotional well-being (Wolfson, 2013; Foster and Roenneberg, 2008).
Of course, it remains to be fully understood how much of our mood-related makeup and behavior is hardwired at birth, and how much of it is determined by outside factors like family, childhood experiences, education, and financial lack or privilege. Regardless, the findings of these studies spark intriguing inquiries regarding what, exactly, it means to experience depression, schizophrenic hallucinations, and swings in emotional state characteristic of bipolar—plus how much can or should be done to prevent these conditions if they are, in fact, imprinted at birth.
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