9(34 BIOLPSYCHIATRY Correspondence 1994:35:963-966 correlation between stimulus intensity and efficacy with bilateral ECT (Robin and deTissera 1982). Riddle et al (1993) did not address the speed of response in their article, and their previous work on hNpl I (Scott et al 1986. 1989, 1991) showed a positive correlation between extent of release of this compound after the first of a series of ECT and "extent of eventual improvement in symptoms of depressive illness over a course of treatment" (Rid- die et a11993, p. 839), that is. ej~cacy. We conclude that it is not yet clear what the release of oxytocin. and its associated neurophysin, reflect in terms of clinical ECT parameters and induced seizure characteristics. We hope that our comments assist the authors in planning their future investigations into this variable. Ralph J. Koek ~¢o/wrtL. Lloyd A/bert Sat/in Department of Psychiatry and Biobehavioral Sciences. UCLA School of Medicine, Sepulveda VA Medical Center. Sepulveda. CA 91343 References Abrams R, Swartz CM, Chandragupta V (1991): Antidepressant effects of high dose right unilateral electroconvulsive therapy. Arch Gen Psychiat~ 48:746--748. Riddle WJR. Scott AIF, Bennie J. Carroll S, Fink G (1993): Current intensity and oxytocin release after electroconvulsive therapy. Biol Psychiatry 33:839-84 I, Robin A, deTissera S (1982): A double-blind controlled compari- son of the therapeutic effects of low and high energy electro- convulsive therapies, BrJ Psychiatr3., 141:357-366. Sackeim HA, Devanand DP, Pmdic J (1991): Stimulus intensity, seizure threshold, seizure duration: impact on the efficacy and safety of electroconvulsive therapy. Psychiat C/in North Am 14:803-844. Sackeim HA (1991): Optimizing unilateral electroconvulsive therapy. Convulsive Therapy 7:201=212. Scott AIF, Whalley JJ, Bennie J, Bowler G (1986); Oestrogen- stimulated neurophysin and outcome after electroconvulsive therapy, Lancet i: 1411-1414. Scott AIF, Whalley LJ, Legros JJ (1989): Treatment outcome, seizure duration and the neurophysin response to ECT, Biol Psychiato, 25:585-597, Scott AIF, Shering A, Legros J J, Whaley LJ (1991): Improvement in depressive illness is not associated with altered release of neurophysins over a course of ECT, Psychat~' Res 36:65-73. Response To the Editor: i thank Dr, Koek and colleagues tbr their interest in our work, but reply simply that recent research findings have clearly shown that stimulus intensity is positively related to the rate of improve- ment in bilateral as well as right unilateral electroconvulsive ther- apy (ECT). Sackeim et al (1993) demonstrated that regardless of electrode placement, high dosage (2.5 x seizure threshold) resulted in more rapid improvement than low dosage (just above the seizure threshold). The failure to detect a relationship between stimulus intensity and clinical outcome in the study by Robin and deTissera (1982) was impossible to assess when these authors did not mea- sure the seizure threshold and the relationship of stimulus intensity to threshold was unknown. The authors do not properly describe the method of clinical assessment in our previous work and ! would point out that clinical improvement was expressed as a change in the severity of depressive illness over a course of ECT, (Scott et a11991, p. 66). 1 am sure the authors are correct that our hypothesis requires further investigation, but I note that they do not suggest an alterna- tive. Our hypothesis is parsimonious and also takes into account the findings of animal studies (Scott et al 1991) that show that the release of oxytocin and its associated neurophysin is closely corre, lated with the rate of electrical activity in these neurons and that electrical stimulation of the hypothalamus increases the concen- tration of oxytocin in the cerebrospinal fluid; moreover, our hy- pothesis is compatible with the finding that the release of the oxytocin-association neurophysin does not change over a course of ECT if stimulus intensity is standard (Scott et al 1991). Alkm I.F, Scott The Andrew Duncan Clinic, Royal Edinburgh Hospital, Edinburgh EHI0 5HF, United Kingdom References Robin A, deTissera S (1982): A double-blind controlled compari- son of the therapeutic effects of low and high energy electro, convulsive therapies, BrJ Psychiatm 141:357-366. Sackeim AH, Prudic J, Devanand DP et al (1993)" Effects of stimulus intensity and electrode placement on the efficacy and cognitive effects of electroconvulsive therapy. N Engl J Med 328:839=846, Scott AIF, Shering A, Legros J J, Whalley LJ (1991): Improve- ment in depressive illness is not associated with altered release of neurophysins over a course of ECT, Psychia,3, Res 36:65- 73, Comment on "Does Oxytocin Release Correlate with ECT's Efficacy?" To the Editor: The paper by Riddle et al (1993) is an important contribution, Using a within-subject design, they confirmed previous sugges- tions that early in the course of electroconvulsivetherapy (ECT) a substantial increase in the intensity of the electrical stimulus pro- duces a shorter duration of cerebral ictal activity (Robin et al 1985; Sackeim et al 1991), Further, this study suggests that despite a shorter seizure duration, a higher intensity of electrical stimulation enhances the release of oxytocin acutely following the seizure discharge. This concurs with preliminary findings from our group indicating that the acute release of vasopressin is sensitive to electrode placement, whereas the acute release of oxytocin is sen- sitive to electrical dosage (Devanand et a11987). Riddle et al (I 993) suggested that the effects of stimulus inten- sity on oxytocin release may account for the relations they