Objective: To investigate the variations of contingent negative variations (CNV), P300 and mismatch negativity (MMN) in patients with obsessive compulsive disorder (OCD), depression and anxiety. Methods: Event- related potentials CNV, P300 and MMN were recorded in 31 patients with OCD by Nicolet Spirit Instrument, and were compared with that of 20 depression controls (DC) and 17 anxiety controls (AC) and 28 normal controls (NC). Results: A significant difference of CNV among 4 subject groups was found in both post- imperative negative variation (PINV) and amplitudes (M1) (P ＜ 0.01 ) (emergence of PINV were 45%,60%, 35%, and 4% in OCD, DC, AC and NC groups respectively). Compared with NC group, DC and AC groups showed decreased M1 amplitude ( P ＜ 0.01). A significant difference of P300 among 4 groups was found in both latencies (Cz/N2) and P3 and nontarget - P2 amplitudes (P ＜ 0.05 ～ 0.01). The delayed MMN latencies of OCD and DC were similar to that of P300 changes. Conclusions: CNV, P300 and MMN are useful tools for assessing the brain malfunction of OCD, DC and AC, and its clinical application are suggested. The characteristics ERPs of those patients might be useful indexes in distinguishing OCD from DC and AC patients.

Analysis of repeated outcome measures from longitudinal studies

In many clinical studies repeated measurements of an outcome are collected over time.For example,in an 8-week study of treatment for obsessive compulsive disorder,the severity of the disorder may be measured weekly using the Yale-Brown-Obsessive-Compulsive-Disorder-Scale (YBOCS).For each study participant who completes the study,there will be nine repeated measures of YBOCS (a baseline assessment plus eight assessments during the course of treatment).Such a study in which participants are followed and measured repeatedly over time is called a longitudinal study and the resulting data are called longitudinal data.