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Which treatments are effective: an epidemiological perspective1

  • Michael G. Gelder (a1)

Objective – To consider some of the problems that may arise when the results of clinical trials are applied uncritically to everyday clinical practice. To show how an epidemiological perspective makes it easier to identify these problems. Method – A review of clinical trials to illustrate problems of: (a) covert selection bias in individual trials, (b) bias in the selection of trials included in reviews and meta-analyses. Results – Several kinds of selection bias are known to exist. In particular, trials with negative results are less likely to be published in widely read journals than are trials of similar scientific quality reporting positive results. Conclusions – There are dangers in applying the results of trials to clinical practice in an uncritical way. These dangers can be avoided by adopting and epidemiological perspective, seeking for clinical trials that are representative of the whole population of trials. The Cochrane Collaboration has been established to minimize biases in reviews and meta-analysis. The first Cochrane Centre on Schizophrenia has been established in Oxford and others are planned.


Scopo - Descrivere alcuni problemi che possono emergere quando i risultati degli studi clinici controllati sono utilizzati acriticamente nella pratica clinica quotidiana e mostrare come una prospettiva epidemiologica faciliti l'identificazione di questi problemi. Metodo - Una rassegna degli studi clinici controllati per illustrare i problemi di: a) nascosta distorsione nella selezione dei casi, nei singoli trial; b) distorsione nella selezione degli studi inclusi nelle rassegne e nelle meta analisi. Risultati - È nota l'esistenza di molti tipi di distorsione nella selezione. In particolare, gli studi clinici con risultati negativi, a paritá di qualita scientifica, hanno minori probability di essere pubblicati su riviste a larga diffusione rispetto agli studi con risultati positivi. Conclusioni - Ci sono dei rischi nell'applicare, in modo acritico, i risultati dei trial alia pratica clinica. Tali rischi sono evitabili adottando una prospettiva epidemiologica e cercando trial clinici che siano rappresentativi dell'intera popolazione dei trial stessi. Il Cochrane Collaboration è stato fondato per minimizzare le deviazioni nelle rassegne e nelle meta analisi. Il primo Cochrane Centre on Schizophrenia è stato istituito ad Oxford ed altri sono previsti.

Corresponding author
Indirizzo per la corrispondenza: Professor M. G. Gelder, University Department of Psychiatry, Warneford Hospital, Oxford OX3 7JX (England). Fax +44 - 1-865.793.101
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Testo della lettura magistrale tenuta al Secondo Congresso Nazionale della Società Italiana di Epidemiologia Psichiatrica (Bologna 12-14 ottobre 1994)

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Epidemiology and Psychiatric Sciences
  • ISSN: 2045-7960
  • EISSN: 2045-7979
  • URL: /core/journals/epidemiology-and-psychiatric-sciences
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