COMT and nicotine dependence: On the other hand, the COMT rs4680 variation (G/A or A/A, the low-activity alleles) was associated with nicotine dependence in men and women of African-American and European-American descent [9], smoking severity among Chinese male smokers [42], heaviness of smoking in Caucasian pregnant women [43], and susceptibility to cigarette smoking among Thai males [11].