Three dependent benzodiazepine users were studied during gradual discontinuation from an initially rather high dosage to zero dose with respect to performance/behaviour in simulated driving and laboratory test performance. Tests were performed before, during and 1-2 months after tapering. Comparisons were made with an individually age- and sex-matched control group of the same size. Power analyses were performed for the different effect measures. For brake reaction time there was a weak tendency for the drug users to show impaired performance initially. For lateral position variation and average speed there was no such tendency. For these three measures there was no tendency for improvement over time. The users tended to have the highest speed variation initially. The difference between users and control subjects was largest during tapering-off and smallest after it. It was calculated that 40 persons per comparison group would be required in order to find this change over time statistically significant at power = .90. For simple reaction time there was no tendency for the users to be impaired initially. There was no tendency for improvement over time either. The users performed poorer in the memory test, which seemed to decrease over time. For choice reaction time there was a difference between the two groups for number of correct responses; the drug users performed worse. There was a tendency that the difference was greatest at the first and smallest at the last test session. For reaction times to correct responses the users tended to be impaired initially. However, there was no tendency for a change over time in the desired direction. Subjective measures were also studied, and the greatest tendency for change was found for fatigue, wakefulness, energy, and, to some extent, well-being. It is concluded that, in general, the tendencies for change in the desired direction are small, especially for performance/behaviour measures. A larger study is proposed where the users will be tested when at least one year has passed since the start of the drug free period. (A)
Samenvatting