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326 B.J. HAVAKI-KONTAXAKI et al PSYCHIATRIKI 21 (4), 2010ated with suicidality. 41 A polygenic inheritance of suicidalbehavior in depressed patients with a history ofsuicide attempts was detected. 44 The occurrence ofsuicidal ideation was a familial component, strongeramong males than females psychiatric patients. 45It is widely accepted that serotonergic dysfunctionpredispose to phenotypes of increased vulnerabilityto traits associated to suicidal behavior (as for exampledisturbed impulse control). Although studieshave reached in many cases contradictory conclusions,many of them offer candidate genes responsiblefor such behavior. One of them is located onchromosome 17 expressing the 5-HT transporter. Afunctional polymorphism (s-allele of 5HTTLPRR) decreasesthe serotonin uptake by lowering the geneexpression, a condition related with neuroticism.Additionally, postmortem findings in suicide victimsdisplay reduction in 5-HT transporter in the region ofprefrontal ventral cortex. 46,47Researchers have associated the low levels in thecerebrospinal fluid of the major 5-HT metabolite (5-hydroxy-indoleacetic acid) with various psychiatricdisorders including depression and suicides. A significantcorrelation between TPOH (limiting enzymein the synthesis of 5-HT and possibly melatonin) andinadequate impulse control has been pointed outelsewhere, suggesting that an intron 7 polymorphismon chromosome 11 in the region of TPOHgene, plays a role in reduction of serotonin turnover.Other, functional or not, allele variants which adjustmechanisms like transporting, secretion or bindingof neurohormones (including melatonin and componentmolecules) in serotonergic and nor-adrenergicsystems have been reported. 48–52 Homozygosity forthe short allele (the frequency of the C-C genotype)is significantly less frequent in unipolar affective disorderpatients with a history of suicide attempt thanin healthy subjects. 53Genetic correlates of seasonal variationin suicide-the SAD patientSeveral studies attempted to reveal a correlationbetween endophenotypes predisposing to suicideand periodic biochemical patterns. TPOH gene’s expressiondisplays different levels of the enzyme activityduring day time with an increase during night.Lower levels of plasma L-tryptophan in spring matchthe annual pattern for suicides. Decreased serotonintransporter binding potential, under a longer photoperiod,may offer an explanation for changes inindividual’s behavior, according to the expected increaseof synaptic 5-HT levels.The observation of hyperactivity of the serotonergicsystem in spring might seem paradoxical sincewe expect lower 5-HT activity during the time ofhigher suicide risk. Moreover, a certain subpopulationof depressed patients seems to get worse insymptoms during the late fall and winter (SeasonalAffective Disorder, SAD). 54–56It may be useful though to keep in mind that mechanisms,such as auto inhibition of 5-HT receptors ondifferent locations in the brain, have been shown toaffect in opposite ways the 5-HT outflow in certainbrain regions.A possible explanation interconnecting the role ofphotoperiod with individual’s mood has been describedsuggesting a triggering effect of sunshine–inshort term– on suicide behavior. 57 Thus, it is plausibleto combine the beneficial impact of sunlight onspirits with the incidence of suicides in spring. Thesame report pointed out a hypothetical model forthe sunshine effect in women and how it can be mediatedby the hypothalamic-pituitary-adrenal axis.Petridou et al 58 confirmed the positive associationbetween month of maximum daylight and higherrelative risk for suicide, stressing the need for furtherinvestigations on how sunshine affects melatoninand melatonin affects mood regulation (not excludingthe role of 5 HT and L-tryptophan in behaviorchanges along with sunshine dependence). The resultswere estimated according to data sent by 20countries for the last 5–24 years. Investigations alsoexist about the role of acute changes in the luminosity,with higher turnover of 5 HT in the brain on brightdays. The pathophysiology may involve traits predisposingto suicidal behavior (aggression and impulsiveness)or hormonal changes, such as suppressionof melatonin due to light accompanied with lack ofsleep. Bjorksten and colleagues 8 reported a significantseasonality in a total of 833 suicides during theperiod 1968–1995 and noted that lifestyle changesduring the arctic summer may cause several disorderslike psychosis, exacerbation of affective disordersand delirium either because of lack of sleep orvia the pre-mentioned changes in 5 HT turnover dueto increased luminosity. The theoretical model of solarradiance, in the long term acting protectively and