research does not support a stronger relationship for either of these alleles compared to the other, and overall differences in research findings are likely more indicative of differences in the populations studied.
In alcoholic offenders an association between the 779C allele and suicide attempt was reported, with multiple attempts related to the number of C alleles (Nielsen et al., 1994). In addition, several studies report an association between the 218C allele and suicide attempt in non-mood-disordered individuals (Nielsen et al., 1998; Paik et al., 2000; Rotondo et al., 1999). In mood-disordered patients compared to healthy controls (Abbar et al., 2001; Bellivier et al., 1998; Tsai et al., 1999) and attempters compared to mood-disordered controls (Mann et al., 1997; Tsai et al., 1999), the A218 Allele was associated significantly with suicide attempt. The association was stronger for violent suicide attempt, especially if there was a history of depression (Abbar et al., 2001), with a dose response of the number of A alleles in one study (Abbar et al., 2001; Mann et al., 1997).
In a study of community volunteers, an association between impulsive aggressive traits and the A218 form of the TPH allele was reported, particularly in men (Manuck et al., 1999). Mann et al. (1997) reported an association between borderline personality disorder and the A218 polymorphism. In a small series of males with personality disorders, New et al. (1998) reported an association between the 218C allele and impulsive aggression.
Serotonin transporter studies. The serotonin transporter has two allelic variants in the promoter regions, a short (S) form and a long (L) form. Exposure to a serotonin agonist activates less transcription of the S than the L form (Greenberg et al., 1999). Comparing suicide victims to controls revealed an association between the L allele and depressed suicides (Du et al., 2000b), between the L allele and depression but not suicide (Mann et al., 2000), and between the S allele and violent suicide (Bondy et al., 2000). Others found no associations (Roy et al., 2001; Turecki et al., 1999). Family based studies on attempts demonstrated a relationship with the S allele, particularly for violent attempts in mood disordered (Bellivier et al., 2000) and alcoholic samples (Gorwood et al., 2000). There was a dose response between the number of S alleles and suicide attempt in those alcoholics with comorbid depression, with no relationship between the number of S alleles and attempts in those alcoholics without depression. On the other hand, Zalsman et al. (2001) reported that the L allele was associated with high measures of aggression. However, Geijer et al. (2000), in a comparison of a diagnostically mixed sample of attempters to healthy controls, found no association.