Efficacy of empirical data in Emotional Wellness (mental health) occurs when constants are measured and changed and legitimacy of the data occurs when it is generated by the client. The constant in Emotional Wellness (mental health) is the clients’ emotional state. Measuring, tacking and improving this constant at every session is what brings about the efficacy of an intervention.
People seek out psychotherapists and psychiatrists because they are emotionally distressed and for no other reason I am aware. For this single reason the answer to the above question should be perfectly clear however when I ask a client this question who has been in therapy for several years there is always a hesitation. The next question I ask is did your therapist measure and track your emotional state. The answer again is no.