Before tumor diagnosis, stressful life events experienced by women with breast cancer are associated with the later development of depressive condi- tions; 5-HTTLPR does not play any significant role. After tumor diagnosis, mental adaptation to cancer is characterized in women with early breast cancer by anxious preoccupation which spontaneously decreases at follow-up; the reduction is significant only in the carriers of the "l/l" 5-HTTLPR genotype. Antidepressants act on depres- sion and mental adaptation to the disease, and the response is genotype dependent. 5-HTTLPR has therefore a role in psycho-oncology, permitting the identification of patients with greater need of support (carriers of "s/s" genotype), and in the case of drug treatment allowing the personalized choice of the drug (benzodiazepines for treating anxiety, or non-SSRI ADs for treating depression in "s/s" patients). Alto- gether, these data are in agreement with the more recent non-oncological reviews, showing a real, though small, effect of 5-HTTLPR on environmental adversity and the action of SSRI antidepressants.