Relationship between alexithymia and event-related potential P300 in patients with somatoform disorders

Objective To investigate the relationship between alexithymia and event-related potential P300 in patients with somatoform disorders.Methods Forty-two patients aged 18 to 65 years fulfilling ICD-10 diagnosis criteria for somatoform disorders were recruited as experiment group.Forty normal healthy persons were selected as control group.The Toronto alexthymia scale-20 (TAS-20) was employed to investigate the alexithymia of the subjects.P300 potentials was employed to investigate the cognitive ability of the subjects.A comparison was made between the patients and the healthy subjects.Results The latencies of N1,P2,N2 and P3 were significantly longer in patients with somatoform disorder than those in the normal controls (P ＜ 0.05 or 0.01),the amplitudes of N2 and P3 were significantly lower in the patients (P ＜ 0.05 or 0.01).The three factors scores and the total score of TAS-20 test in patients with somatoform disorder were significantly lower than those in the normal controls (P ＜ 0.05 or 0.01).There was significant correlation between the latency and the three factors scores and the total score of TAS-20 as well as between the amplitude of P300 and the three factors scores and the total score of TAS-20:the latencies of N1,P2,N2 and P3 recorded at Pz was positively correlated with the factors scores (r =0.32 ～ 0.48,P ＜ 0.05 or 0.01),and the amplitudes of N1,P2,N2 and P3 recorded at Pz was negatively correlated with theTAS-20 scores (r=-0.31 ～-0.51,P＜0.05 or0.01).Conclusions There existed significant correlation between the alexithymia and cognitive impairment in patients with somatoform disorders.Both alexithymia and event-related potential P300 can be used as a clinical evaluation index for patients with somatoform disorder. Key words: Somatoform disorders;  Alexithymia;  Cognitive function;  Event-related potential P300; Toronto alexthymia scale-20