Institute for Response-Genetics (e.V.)

Prof. Dr. Hans H. Stassen, Chairman

(Formerly Associated Institute of the University of Zurich)

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Assessing Onset of Improvement under Antidepressants

Response Criteria

Conventional repeated measurements analysis of variance suggests that response to antidepressants is slow, and that differences between antidepressants and placebo do not normally reach statistical significance until the third to fourth week of treatment. This statistical "response lag" has finally led to the "delayed onset of action" hypothesis, although response-to-treatment and onset-of-action represent two principally different concepts that relate to different aspects of efficacy of antidepressant drug therapy. While efficacy in terms of response-to-treatment has its main focus on the proportion of patients in whom antidepressants induce therapeutic response, onset-of-action refers to the speed at which symptoms reduce under antidepressants in comparison to placebo. Standard drug trial procedures tend to obscure differences in onset of action across drugs (as well as across patients), because such procedures rely upon mean depression scores derived from studies which amalgamate separate depressive subgroups, rapid and slow remitters, as well as partial remitters, non-remitters and premature withdrawals.

Survival Analysis and Cure Models

In the conventional repeated mesurements approach, psychopathology scores assessed at weekly intervals are analysed as a function of time, and assessment times are represented as fixed independent variables in a (linear) regression model when testing for time differences in rates of symptom reduction. This is equivalent to a regression of the sample’s mean scores on assessement time, so that a justification of the "fast acting" claim of the newer antidepressants is, from the methodological point of view, difficult to accomplish. An alternative approach is survival analysis where time is treated as a function of symptom reduction (dependent variable). This has the advantage that variations around the prespecified, cross-sectional observation days (typically ±2 days) can be incorporated into the model, thus providing (1) a better temporal resolution with respect to the individual course of recovery from depression, (2) a way to distinguish between early and late responders, and (3) the possibility to assess the predictive value of early improvement with respect to later outcome. Additionally, the method allows one to take into account that treatment response has not been observed in a subgroup of patients due to premature withdrawal or the limited observation time.

Early Improvement

Central to all approaches to determining early onset of antidepressant action is the appropriate definition of improvement (used as indicator of a specific drug action). We distinguish between "relative improvement", defined by a percentage baseline score reduction regardless of the subsequent course of depressive illness that may include a significant deterioration; "sustained relative improvement", which requires a prespecified percentage baseline score reduction without subsequent deterioration beyond achieved improvement score; "sustained absolute improvement", which requires a prespecified percentage baseline score reduction along with the attainment of a prespecified threshold value (e.g. HAMD-17 score of 10) without subsequent deterioration.


Stassen HH, Bachmann S, Bridler R, Cattapan K, Herzig D, Schneeberger A, Seifritz E: Detailing the Effects of Polypharmacy in Psychiatry: Longitudinal Study of 320 Patients Hospitalized for Depression or Schizophrenia. Eur Arch Psychiatry Clin Neurosci. 2021, doi: 10.1007/s00406-021-01358-5 [epub ahead of print] [get the article]
Moragrega I, Bridler R, Mohr C, Possenti M, Rochat D, Sanchez Parramon J, Stassen HH: Monitoring Mental Health and the Effects of Therapeutic Interventions through Self-Assessment Voice Analyses. Res Psychother. 2021, 24(3): 250-262 [get the article]
Stassen HH, Bachmann S, Bridler R, Cattapan K, Herzig D, Schneeberger A, Seifritz E. Inflammatory Processes linked to Major Depression and Schizophrenic Disorders and the Effects of Polypharmacy in Psychiatry: Evidence from a longitudinal Study of 279 Patients under Therapy. Eur Arch Psychiatry Clin Neurosci. 2021; 271(3): 507-520 [get the article]
Greil W, de Bardeci M, Seifert J, Bernegger X, Cattapan K, Stassen H, Wagner AL, Sieberer M, Grohmann R, Toto S: Treatment of depression: Are psychotropic drugs appropriately dosed in women and in the elderly? Dosages of psychotropic drugs by sex and age in routine clinical practice. Hum Psychopharmacol. 2021, doi: 10.1002/hup.2809 [epub ahead of print]
Pollak TA, Lennox B, Müller S, Benros ME, Prüss H, Tebartz van Elst L, Klein H, Steiner J, Frodl T, Bogerts B, Tian L, Groc L, Hasan A, Baune BT, Endres D, Haroon E, Yolken R, Benedetti F, Halaris A, Meyer J, Stassen H, Leboyer M, Fuchs D, Otto M, Brown DA, Vincent A, Najjar S, Bechter K: An international consensus on an approach to the diagnosis and management of psychosis of suspected autoimmune origin: the concept of autoimmune psychosis. Lancet Psychiatry 2020; 7(1): 93-108
Zhang M, Bridler R, Mohr C, Moragrega I, Sun N, Xu Z, Yang Z, Possenti M, Stassen HH: Early Detection of the Risk of Developing Psychiatric Disorders: A Study of 461 Chinese University Students under Chronic Stress. Psychopathology 2019; 52(6): 367-377 [get the article]
Bhake R, Kluckner V, Stassen HH, Russell GM, Leendertz J, Stevens K, Linthorst ACE, Lightman S: Continuous Free Cortisol Profiles — Circadian Rhythms in Healthy Men. J Clinical Endocrinology & Metabolism 2019; 104(12): 5935-5947
Stassen HH, Bachmann S, Bridler R, Cattapan K, Herzig D, Höppner K, Schneeberger A, Seifritz E, Wirth A, M. Weisbrod M: Polypharmacy in Psychiatry: Unwanted Side Effects and Inflammatory Response System — A Naturalistic Study of 195 Patients under Treatment. Eur Neuropsychopharmacology 2019; 29 Suppl 1: S345
Greil W, Zhang X, Stassen HH, Grohmann R, Bridler R, Hasler G, Toto S, Bleich S, Kasper S: Cutaneous adverse drug reactions to psychotropic drugs and their risk factors — a case-control study. Eur Neuropsychopharmacol. 2019; 29(1): 111-121 [get the article]
Stassen HH: Heterogeneity of schizophrenic disorders and link to chronically elevated IgM values. Neurology, psychiatry and brain research 2018; 29: 23-24
Stassen HH, Braun S, Bridler R, Seifritz E, Weisbrod M: Inflammatory Processes and Schizophrenia: Evidence from a Twin Study. Eur Neuropsychopharmacology 2017; 27 Suppl 4: S934-S935
Braun S, Bridler R, Müller N, Schwarz MJ, Seifritz E, Weisbrod M, Zgraggen A, Stassen HH: Inflammatory Processes and Schizophrenia: Two Independent Lines of Evidence from a Study of Twins Discordant and Concordant for Schizophrenic Disorders. European Archives of Psychiatry and Clinical Neuroscience 2017; 267: 377-389 [get the article]
Braun S, Annovazzi C, Botella C, Bridler B, Camussi E, Delfino JP, Mohr C, Moragrega I, Papagno C, Pisoni A, Soler C, Seifritz E, Stassen HH: Assessing Chronic Stress, Coping Skills and Mood Disorders through Speech Analysis. A Self-Assessment "Voice App" for Laptops, Tablets, and Smartphones. Psychopathology 2016; 49(6): 406-419 [get the article]
Delfino JP, Barragán E, Botella C, Braun S, Bridler R, Camussi E, Chafrat V, Lott P, Mohr C, Moragrega I, Papagno C, Sanchez S, Seifritz E, Soler C, Stassen HH: Quantifying Insufficient Coping Behavior under Chronic Stress. A cross-cultural study of 1,303 students from Italy, Spain, and Argentina. Psychopathology 2015; 48: 230-239
Mohr C, Braun S, Bridler R, Chmetz F, Delfino JP, Kluckner VJ, Lott P, Schrag Y, Seifritz E, Stassen HH: Insufficient Coping Behavior under Chronic Stress and Vulnerability to Psychiatric Disorders. Psychopathology 2014; 47: 235-243
Stassen HH, Delfino JP, Kluckner VJ, Lott P, Mohr C: Vulnerabilität und psychische Erkrankung. Swiss Archives of Neurology and Psychiatry 2014; 165(5): 152-157
Giegling I, Balzarro B, Porcelli S, Schäfer M, Hartmann AM, Friedl M, Konte B, Krämer P, Möller HJ, De Ronchi D, Stassen HH, Serretti A, Rujescu D: Influence of ANKK1 and DRD2 polymorphisms in response to haloperidol. Eur Arch Psychiatry Clin Neurosci. 2013; 263(1): 65-74
Bridler R, Orosz A, Cattapan K, Stassen HH: In Need of Psychiatric Help - Leave a Message after the Beep. Psychopathology. 2013; 46(3): 201-205
Drago A, Giegling I, Schäfer M, Hartmann AM, Friedl M, Konte B, Möller HJ, De Ronchi D, Stassen HH, Serretti A, Rujescu D: AKAP13, CACNA1, GRIK4 and GRIA1 genetic variations may be associated with haloperidol efficacy during acute treatment. Eur Neuropsychopharmacol. 2013; 23(8): 887-894
Drago A, Giegling I, Schäfer M, Hartmann AM, Möller HJ, De Ronchi D, Stassen HH, Serretti A, Rujescu D: No association of a set of candidate genes on haloperidol side effects. PLoS One. 2012; 7(10): e44853
Giegling I, Drago A, Dolzan V, Plesnicar BK, Schäfer M, Hartmann AM, Sander T, Toliat MR, Möller HJ, Stassen HH, Rujescu D, Serretti A: Glutamatergic gene variants impact the clinical profile of efficacy and side effects of haloperidol. Pharmacogenet Genomics. 2011; 21(4): 206-216
Kemp DE, Ganocy SJ, Brecher M, Carlson BX, Edwards S, Eudicone JM, Evoniuk G, Jansen W, Leon AC, Minkwitz M, Pikalov A, Stassen HH, Szegedi A, Tohen M, Van Willigenburg AP, Calabrese JR: Clinical value of early partial symptomatic improvement in the prediction of response and remission during short-term treatment trials in 3369 subjects with bipolar I or II depression. J Affect Disord. 2011; 130(1-2): 171-179
Stassen HH, Anghelescu IG, Angst J, Böker H, Lötscher K, Rujescu D, Szegedi A, Scharfetter C: Predicting Response to Psychopharmacological Treatment. Survey of Recent Results. Pharmacopsychiatry 2011; 44: 263-272
Lötscher K, Anghelescu IG, Braun S, Bridler R, Stassen HH: Polypharmacy in psychiatry: clinical practice versus empirical evidence. Eur Neuropsychopharmacol. 2010; 20 (Suppl. 3): 378-379
Szegedi A, Jansen WT, Van Willigenburg AP, Van der Meulen E, Stassen HH, Thase ME: Early improvement as a predictor of treatment outcome in patients with major depressive disorder: Why the first 2 weeks really matter - evidence from 6562 patients. J Clin Psychiatry 2009; 70(3): 344-353
Stassen HH, Angst J, Hell D, Scharfetter C, Szegedi A: Is there a common resilience mechanism underlying antidepressant drug response? Evidence from 2848 patients. J Clin Psychiatry 2007; 68(8): 1195-1205
Stassen HH, Scharfetter C: Vulnerability, resilience and response to psychotropic drugs: shared genetic factors? Am J Med Genetics 2006; 141: 707-708
Lavergne F, Berlin I, Gamma A, Stassen H, Angst J: Onset of improvement and response to mirtazapine in depression: a multicenter naturalistic study of 4771 patients. Neuropsychiatric Disease and Treatment 2005; 1(1): 59-68
Stassen HH, Angst J, Scharfetter C, Szegedi A: Therapie mit Antidepressiva: Erfolg von genetischen Faktoren abhängig? Leading Opinions, Neurologie & Psychiatrie 2005; 6: 25-27
Stassen HH, Angst J: Wirkung und Wirkungseintritt in der Antidepressiva-Behandlung. Medizinspektrum 2004; 15: 15-17
Stassen HH, Dahmen N, Hell D, Nürnberg P, Sander T, Toliat MR, Szegedi A: Genetic predisposition of antidepressant drug response. Am J Med Genetics 2003; 122: 123-124
Montgomery SA, Bech P, Blier P, Moller HJ, Nierenberg AA, Pinder RM, Quitkin FM, Reimitz PE, Rosenbaum JF, Rush AJ, Stassen HH, Thase ME: Selecting methodologies for the evaluation of differences in time to response between antidepressants. J Clin Psychiatry 2002; 63(8): 694-699
Stassen HH, Angst J, Delini-Stula A: Fluoxetine versus moclobemide: cross-comparison between the time course of improvement. Pharmacopsychiatry 1999; 32: 56-60
Stassen HH, Kuny S,. Hell D: The speech analysis approach to determining onset of improvement under antidepressants. Eur Neuropsychopharmacology 1998; 8,4: 303-310
Stassen HH, Angst J, Delini-Stula A: Onset of improvement under fluoxetine and moclobemide. Eur Psychiatry 1998; 13,3: 128-133
Angst J, Stassen HH: Methodische Probleme der Prüfung von Antidepressiva. In: Stieglitz RD, Fähndrich E, Möller HJ (eds): Syndromale Diagnostik psychischer Störungen. Hogrefe, Göttingen 1998: 5-12
Stassen HH, Angst J, Delini-Stula A: Delayed onset of action of antidepressant drugs? Survey of results of Zurich meta-analyses. Eur Psychiatry 1997; 12: 166-176
Stassen HH, Angst J, Delini-Stula A: Delayed onset of action of antidepressant drugs? Survey of results of Zurich meta-analyses. Pharmacopsychiatry 1996; 29: 87-96
Kuny S, Stassen HH: Cognitive performance in patients recovering from depression. Psychopathology 1995; 28: 190-207
Stassen HH, Angst J: Methods of estimating onset of improvement. Eur Neuropsychopharmacology 1994; 4,3: 284-285
Stassen HH, Angst J, Delini-Stula A: Severity at baseline and onset of improvement in depression. Meta-analysis of Imipramine and Moclobemide vs Placebo. Eur Psychiatry 1994; 9: 129-136
Stassen HH, Delini-Stula A, Angst J: Time course of improvement under antidepressant treatment: a survival-analytical approach. Eur Neuropsychopharmacol 1993; 3: 127-135
Angst J, Delini-Stula A, Stabl M, Stassen HH: Is a cutoff score a suitable measure of treatment outcome in short-term trials in depression? A methodological meta-analysis. Human Psychopharmacology 1993; 8: 311-317
Angst J, Stassen HH, Woggon B: Effect of neuroleptics on positive and negative symptoms and the deficit state. Psychopharmacology 1989; 99: 41-46


Cure Models: Assessing Onset of Improvement under Antidepressants
One-dimensional cure models combine "incidence" and "latency" in one single model. The distribution of the times to onset of improvement under imipramine (circles, n=506), moclobemide (triangles, n=580) and placebo (squares, n=191) suggest significant between-treatment differences.
By contrast, 2-dimensional cure models distinguish between "incidence" and "latency". Results show that the observed differences can almost entirely be explained by "incidence" (>90%) whereas "latency" explains less than 10%.
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