About 5-10% of people actually get worse after starting psychotherapy. Studies comparing therapists who got feedback when their clients worsened showed that their clients did better than those people with therapists who were left to carry on regardless - suggesting that not all therapists know when their clients are going downhill. Researchers from the Indiana University of Pennsylvania looked into this issue by giving questionnaires to clients to assess their mental state and comparing them with the therapists' own notes. They found that 'therapists had considerable difficulty recognising client deterioration.' Other therapists were asked how they would judge if a client was going downhill and most replied that they would judge from their clients' symptoms rather than using a standardised rating scale. The most popular options for what to do if a client worsened were to make a referral for medication, to increase the frequency of therapy sessions, to gather more information, to discuss the deterioration with the client, to counsult other therapists and to change the treatment approach in some way.
Hatfield, Derek ... [et al] - Do we know when our clients get worse? An investigation of therapists' ability to detect negative client change Clinical Psychology and Psychotherapy January-February 2010, 17(1), 25-32