Such data reduction is no easy task. In order to make the patient variables searchable, some major reduction of the data is a must. Although not an easy task, this seems possible by turning to the outcome literature and asking what patient variables have been shown in the past to matter. A parallel problem of data reduction holds for outcome variables, but again, it seems possible in the same way. There is a very large number of such treatment variables, but again, these might be reduced to several score.
Case histories are notoriously selective .
One writes about successful case histories in which treatments work, in which a theory is confirmed, or in which a rare disorder presents, but one does not usually write up treatment failures, the failures of a technique within a treatment, or tedious cases. In order for this database to be useful, the problems of selection for positive outcomes, selection for theory confirmation, selection for positive techniques within a treatment, selection for the dramatic, and selection for only the elements that confirm one's biases must be overcome. The database must include failure experiences as well as success experiences, blind alleys, alternative biases, and tedious cases. Related to the problem of selectivity is the problem of inferring etiology. Case histories are poor material for making causal inferences about etiology.