ObjectivesThe aim of this longitudinal intervention study was to assess the impact of psychosocial stress and coping response strategies on the clinical outcomes in periodontitis patients treated with non-surgical periodontal therapy (NSPT).Materials and methodsAfter the administration of psychological questionnaires, patients diagnosed with generalized stage III–IV periodontitis were categorized into different groups depending on their stress levels (10-item perceived stress level (PSS-10)) and coping response strategies (coping responses inventory (CRI)). Clinical data were collected 1 week before and 3 months after the completion of NSPT.ResultsOf the 90 patients included at baseline, 27 presented major and 63 minor stress levels, while 40 had avoidance and 50 approach coping behavior. All clinical parameters were similar at the baseline across different categories. At re-evaluation, full-mouth bleeding score (FMBS), mean probing pocket depth (PPD), and number of residual pathological pockets were significantly superior in groups with higher stress levels (p<0.001,p=0.001, andp=0.020, respectively), while higher full-mouth plaque scores (FMPS) and FMBS were found in patients with avoidance coping strategies (p=0.009 andp<0.001, respectively). When jointly evaluated, an added detrimental effect of coping styles on allostatic load was observed. Multivariate analysis confirmed a significant effect of stress levels and coping strategies on final FMBS, but not of coping on mean PPD.ConclusionPsychosocial stress and avoidance coping strategy seem to negatively influence the clinical outcomes of NSPT at short term (NCT04739475; 9/1/2017).Practical implicationsBased on these findings, patients reflecting these psychological profiles should be considered at greater risk for poor NSPT response and may benefit from complementary stress management strategies.