Among primary care attendees the CIDI is a highly valid assessment of common mental disorders, and the CIS-R is moderately valid. Previous studies may have underestimated validity. Against the criteria of all ICD-10 diagnoses (including less severe depressive and anxiety disorders) a much lower CIS-R cut-point is required than that which is usually advocated.

Prolonged treatment and neonatal unit stay are influenced by the type of maternal drug abused.

Neonatal abstinence syndrome (NAS) is suffered by infants withdrawing from substances on which they have become physically dependent after in utero exposure. They may require prolonged treatment and spend weeks or even months in hospital. A wide range of drugs have been used to treat NAS. The efficacy of few, however, have been adequately investigated. Evidence suggests that opioids are the most appropriate, at least in infants exposed to diamorphine or methadone. In all "head to head" trials, diazepam has been shown to be ineffective. Morphine and methadone are currently the most commonly prescribed opioids to treat NAS, but randomised trials have not been undertaken to determine which is the more beneficial. Many infants with NAS have been exposed to multiple substances in utero. Further research is required into whether a single opiate or a multiple drug regimen is the best option for such patients.

The use of illicit substances such as cocaine and heroin during pregnancy is common. Anonymous screening of consecutive urine samples testing positive for pregnancy from a UK inner-city clinic demonstrated that approximately 16% of the women had taken one or more illicit substances (Sherwood et al, 1999). The prevalence of drug misuse in the USA appears to be even higher: prospective screening of newborns in a high-risk urban population revealed that 44% of 3010 babies tested positive for opiates, cocaine or cannabis (Ostrea et al, 1992). The aim of this editorial is to emphasise the importance of this topic by describing the unfavourable effects illicit substances can have on both pregnancy and infant outcome. In addition, discussion of the evidence base for current management highlights the need for appropriately designed studies to optimise treatment and reduce morbidity.

About 30% of adults in Britain have used illicit drugs at some time in their lives, but misuse of prescription drugs (such as benzodiazepines and barbiturates) is probably even more widespread. Cannabis is the most commonly used illicit drug. About 100 000 people misuse heroin (diamorphine), and an unknown but increasing number use other drugs such as ecstasy and amphetamines. While the number of new drug users continues to rise, the number who inject drugs is falling, possibly as a result of health education about risks of HIV transmission. The highest number of addicts are found in London and the north west of England.