DEPRESSION AMONG THE HEAD-INJURED AND NON-HEAD-INJURED - A DISCRIMINANT-ANALYSIS

Neuropsychologists often use traditional psychological tests to assess depression following a head injury; but the assumption that depressio n with a head injury resembles that in an uninjured person is suspect. The current study attempts to examine the cognitive manifestations of depression with and without a coexisting head-injury. Advanced statis tical methods are used to assess whether or not the two depressions 'l ook alike' with respect to the neuropsychological sequelae of the diso rders. A total of 1182 people were entered into one of two discriminan t function analyses (DFA) for depression. Each person was a member of one of the following groups: (a) depressed, (b) non-depressed, (c) hea d-injured, or (d) head-injured and depressed. Two functions were perfo rmed for depression, one on the population of head-injured people and one on the population of uninjured people. Cross-validations were perf ormed for each population and across populations in order to assess th e utility of each population's function for the opposite group. This c omparison allows the researcher to indirectly compare depression in th e two populations. Both functions were successfully applied to either population when MMPI variables were included in the analyses. However, when only cognitive variables were included the function performed on the non-head-injured population did not correctly classify head-injur ed people as depressed or non-depressed. One explanation for this is t hat the range of cognitive scores in head-injured people is so great t hat it allows for a less accurate but more generalizable function. Sug gestions for future research are discussed.