Eur Arch Psychiatry Clin Neurosci (2002) 252 : 130 –134 DOI 10.1007/s00406-002-0372-7 ■ Abstract Separate studies on adults, including those in suicidology and another regarding personality in the general population, have indicated associations with their season of birth.We analyse each of these studies by multiple nonlinear regression employing a cosine func- tion for the month of birth, and compare these studies regarding the birth months giving the maxima and min- ima. The method of suicide in suicide studies shows a significant month-of-birth variation similar to that for the serotonin metabolite 5-HIAA in the separate study on cerebrospinal fluid, with a peak around the birth month September and a nadir around birth in March. When comparing the personality study with the study on cerebrospinal fluid, the trait novelty seeking varies similar to that for the dopamine metabolite HVA or the norepinephrine metabolite MHPG, and the trait reward dependence varies similar to that for HVA.The trait self- transcendence varies similar to the ratio of the dopamine and serotonin metabolites. Dopamine turnover in adults thus shows a peak around the birth months November-December, and a nadir around the birth months May-June, suggesting a possible involve- ment of the length of photoperiod during their perina- tal period. These results provide strong evidence for the influence of season of birth on adult monoamine neuro- transmitter turnover, and give further support for the monoaminergic modulation of the temperament and character traits. ■ Key words Season of birth · serotonin · dopamine · norepinephrine · personality · suicide method ORIGINAL PAPER Jayanti Chotai · Rolf Adolfsson Converging evidence suggests that monoamine neurotransmitter turnover in human adults is associated with their season of birth Received: 14 November 2001 / Accepted: 20 May 2002 EAPCN 372 Introduction Season of birth is known to be associated with several psychiatric and neurological disorders in adults (Torrey et al. 1997). Other season-of-birth associations have also been reported. For example, population studies regard- ing adult life expectancy have shown that those born in the northern hemisphere during October to December live longer than those born during April to June, and the pattern is shifted half a year in the southern hemisphere (Doblhammar and Vaupel, 2001). This suggests that the circumstances around the gestational and perinatal pe- riod may be modulating several neurodevelopmental aspects, likely involving also the development of the monoamine neurotransmitter systems, with long-term effects extending into adulthood. The rate of turnover of the monoamine neurotrans- mitters dopamine, serotonin, and norepinephrine in the central nervous system are known to be influenced by genetic as well as environmental factors (Clarke et al. 1996; Higley et al. 1993; Schneider et al. 1998; Reznikov et al. 1999; Herlenius and Lagercrantz 2001). Since cere- brospinal fluid (CSF) levels of their metabolites ho- movanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA), and 3-methoxy–4-hydroxyphenylglycol (MHPG),respectively,are generally positively correlated with the turnover of the corresponding monoamines, these levels are often used as indicators of their turnover. It was found in a clinical sample of adult patients with the psychiatric diagnoses of mood, anxiety, or adjust- ment disorder, that their CSF levels of the metabolites 5- HIAA and HVA showed an association with their season of birth (Chotai and Åsberg 1999). Those born during February to April had significantly lower levels of 5- HIAA, and those born during October to January had significantly higher levels of HVA, as compared to birth during the rest of the year. In another study analysing a register of completed suicides during the period 1952–1993 from another part Jayanti Chotai, MD, PhD () · R. Adolfsson Division of Psychiatry University Hospital 90185 Umeå, Sweden. Tel.: +46-90/7 85-00 00 Fax: +46-90/13 53 24 E-Mail: jayanti.chotai@vll.se