How can behavior therapy treat the same disorder with different techniques and different disorders with the same technique?

Traditional psychiatric diagnostic labels fail to differentiate patients on the basis of the function of the problematic behavior because such labels do not specify the nature of the individual's behavioral deficits or excesses. In contrast, behavior therapy strives to classify clinical phenomena based upon their functional characteristics guided by theoretical considerations. Yet, the anomaly exists that for a given disorder there is frequently a long list of suggested treatments that all have some degree of demonstrated efficacy. Similarly, there are a number of apparently different disorders that have been successfully treated with the same general technique. The implications of this paradox will be discussed in the context of treatments for depression. Our recent work suggests that different types of depression respond to different interventions depending on whether interventions match or do not match those types.