Exactly, which is why I support the National Institutes of Mental Health's (NIMH) efforts to move away from the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), which is just a dictionary of subjective labels for collections of mental health symptoms, to the Research Domain Criteria (RDoC), which is a matrix of measures that place patients along a variety of psychological spectrums to understand their mental illness [1]:

While DSM has been described as a “Bible” for the field, it is, at best, a dictionary, creating a set of labels and defining each. The strength of each of the editions of DSM has been “reliability” – each edition has ensured that clinicians use the same terms in the same ways. The weakness is its lack of validity. Unlike our definitions of ischemic heart disease, lymphoma, or AIDS, the DSM diagnoses are based on a consensus about clusters of clinical symptoms, not any objective laboratory measure. In the rest of medicine, this would be equivalent to creating diagnostic systems based on the nature of chest pain or the quality of fever. Indeed, symptom-based diagnosis, once common in other areas of medicine, has been largely replaced in the past half century as we have understood that symptoms alone rarely indicate the best choice of treatment.

In contrast with the vastly superior RDoC Matrix [2]:

The RDoC research framework can be considered as a matrix whose rows correspond to specified dimensions of function; these are explicitly termed “Constructs,” i.e., a concept summarizing data about a specified functional dimension of behavior (and implementing genes and circuits) that is subject to continual refinement with advances in science. Constructs represent the fundamental unit of analysis in this system, and it is anticipated that most studies would focus on one construct (or perhaps compare two constructs on relevant measures). Related constructs are grouped into major Domains of functioning, reflecting contemporary thinking about major aspects of motivation, cognition, and social behavior; the five domains are Negative Valence Systems (i.e., systems for aversive motivation), Positive Valence Systems, Cognitive Systems, Systems for Social Processes, and Arousal/Regulatory Systems. The columns of the matrix represent different classes of variables (or units of analysis) used to study the domains/constructs. Seven such classes have been specified; these are genes, molecules, cells, neural circuits, physiology (e.g. cortisol, heart rate, startle reflex), behaviors, and self-reports. Circuits represent the core aspect of these classes of variables – both because they are central to the various biological and behavioral levels of analysis, and because they are used to constrain the number of constructs that are defined. Investigators can select any level of analysis to be the independent variable for classification (or multiple levels in some cases, e.g., behavioral functioning stratified by a genetic polymorphism), and dependent variables can be selected from multiple columns. In addition, since constructs are typically studied in the context of particular scientific paradigms, a column for “paradigms” has been added; obviously, however, paradigms do not represent units of analysis.

[1] http://www.nimh.nih.gov/about/director/2013/transforming-dia...

[2] http://www.nimh.nih.gov/research-priorities/rdoc/index.shtml