Stewart’s work followed up findings by PhD graduate, Tharaka Dassanayake, who found that such patients, even though considered clinically recovered, were still impaired cognitively at discharge in functions important for driving (see the publications both here and here). In a subsequent data-linkage study, Tharaka found that overdosed patients are 3-4 times more prone to a traffic accident during the first 2-3 days and 1.5 times during the first four weeks (see here). What was most surprising was that there was still an increased risk of a traffic accident up to 4-weeks following discharge.
It was this puzzle that Stewart’s project followed-up by studying the pattern of cognitive recovery in patients who overdosed with sedatives compared to a group who overdosed with non-sedative drugs. Although both groups improved over the following month, the sedative group's recovery was slower for cognitive functions underlying driving. Other variables (e.g., mood, medication and/or medication changes) could not explain slower cognitive recovery.
Patients could have impaired driving for at least 3 days, and possibly up to one week following sedative overdose. Simple cognitive tests (such as Trail-Making B) could be used to assess their fitness to drive.
This research was co-supervised by Pat Michie and Mater collaborators - Greg Carter, Alison Jones, and Ian Whyte. Gavin Cooper’s technical support was invaluable. Tharaka has now returned to the Department of Physiology, University of Peradeniya, Sri Lanka. Stewart is completing his clinical registration and working as a psychologist in a private practice and for an employment service. We wish them both every success in their future careers.
