Symptom over- and underreporting are relatively stable behavioral opposites in forensic patients and undergraduates

The phenomena of symptom overreporting, underreporting, and inattentive responding have often been linked to traits using cross-sectional designs. The preliminary question - the temporal stability of these phenomena - has remained largely unexamined. We conducted a test-retest study in forensic inpatients and students (all ns >= 64), who twice - across a six- to ten-week interval - completed stand-alone measures of symptom overreporting, symptom underreporting, inattentive responding, and Big Five personality domains. Symptom overreporting rates were similar in patients and students (+5 %). The same was true for symptom underreporting in patients (+15-20 %) and students (+5-10 %), whereas inattentive responding was non-trivial in patients (+15 %), but low in students (+0-5 %). In both groups, symptom overreporting and underreporting were relatively stable behavioral opposites. Trait scores of those who engaged in symptom overreporting and underreporting deviated +0.75 SD from those who passed all validity indices, and in a patterned rather than arbitrary way. The shared variance may reflect a common underlying mechanism. In patients, borderline personality disorder was linked to symptom overreporting, whereas narcissistic personality disorder was associated with symptom underreporting. Overall, our findings suggest that both traits and contextual factors shape how accurately people report their symptoms.