Introduction: While there are many publications reviewing the principles of informed consent (IC), there are little data to indicate if the absence of informed consent affects the outcome of Randomised Controlled Trials (RCT's). This study aimed to assess RCT's in The Australian and New Zealand Journal of Psychiatry (ANZJP) with regard to explicit reporting of informed consent (IC). Issues related to inclusion of studies that have not reported that IC was gained are discussed. Some clinical trials are still undertaken where there is doubt about the quality of the informed consent obtained. This neglect may introduce biases into systematic reviews. There is little empirical evidence to support this. However studies are suggestive and indicate the need for further research.

Methods: The ANZCP was hand searched for RCT's from 1967 -1995. All RCT's were inspected in order to determine whether IC was reported. 43 RCT's were identified. 10 reported that informed consent was obtained and 33 did not. There was a statistically significant improvement in reporting over time.

Discussion: IC is poorly reported in the ANZJP. Comparative studies from other psychiatric journals show even poorer results. The necessity of obtaining informed consent introduces a potential sampling bias. Only those patients who can and are willing to consent are included in RCTs. Evidence suggests that this may be a more compliant group than those who do not enrol. These diverse groups potentially introduce a source of heterogeneity into attempts to combine RCTs in which consent was obtained and in which it was not. There is a moral argument to exclude RCT's from systematic reviews which do not report IC. If consent was not obtained from patients involved in RCTs should that data be used in systematic reviews i.e. is science which is only potentially unethical "bad science"?