This case-control study (n = 100 dental patients, matched for age and sex) investigated the role of life-events in periodontitis. Data collected included life events, tobacco use, oral health behaviours and socio-demographics. The results of conditional simple logistic regression analysis showed that periodontitis was associated with the negative impact of life-events (p < 0.01), the number of negative life-events (p < 0.05), high levels of dental plaque (p < 0.01), tobacco smoking (p < 0.01) and being unemployed (p < 0.05). These associations remained statistically significant after adjusting for oral health behaviour and socio-demographic variables, but not tobacco smoking (p > 0.05). Marital status became statistically significant after adjusting for the other variables (p < 0.05). A model is suggested to explain the pathways through which life events may affect periodontal health. It was concluded that psychosocial factors and oral health risk behaviours cluster together as important determinants of periodontitis.