The following resources may be of interest to you.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2719446/

http://www.ncbi.nlm.nih.gov/pubmed/12858428

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CEEQFjAD&url=http%3A%2F%2Fmedhealth.leeds.ac.uk%2Fdownload%2F666%2Freport_on_the_evidence_base_of_systemic_family_therapy&ei=KjSKVZnaNYq5oQSUxaX4Dw&usg=AFQjCNEkfxCQZqGnkKwZbFrzOPFvwxoukQ&sig2=UdjQUQXoFvTAGfRsH00BKg&bvm=bv.96440147,d.cGU

Thank you, Stephen. Yet, I am not convinced that adding family therapy to TAU (antidepressants and/or individual psychotherapy) improves efficiency in depressed (not bipolar) adults (who do not have marital problems)... Either no research has focused on that, or studies resulted in null-findings that were not published. Have we identified another gap between clinical practice and theory/research?

Thanks for your insightful comments and questions, Kris. Yes, there is a gap between family therapy practice and research.

Richard Niolon (2011) summarized some of the challenges and findings in family therapy research:

"...So Does Family or Couples Therapy Work?

...Pinsoff and Wynne (2000) answer that family and/or couples therapy is better than individual therapy for:

schizophrenia

depression in women in distressed marriages

marital distress

adult substance abuse

adolescent conduct disorders and substance abuse

anorexia in young females

childhood autism

aggression and non-compliance in ADHD children

dementia

and cardiovascular risk factors

and is better than no treatment for all of the above in addition to

obesity

hypertension

child conduct disorder

and chronic illness in childhood

Gurman and colleagues (in Garfield and Bergin) would add “medical” disorders (like eating disorders, diabetes, and asthma), anxiety, and phobias to the list of problems that benefit more from family or couples therapy than individual therapy. Gurman and colleagues offer that, generally, about two thirds of clients in any kind of family therapy get better, which is fairly similar to the numbers gained in individual therapy intervention research. They would add more specifically that:

Better gains are found when both members of a couple work on marital problems.

Better gains occur when the therapist is more active in the early phases of therapy.

Basic mastery of the theory and techniques by the therapist seems enough to halt deterioration, but more skill by the therapist is required for positive growth in therapy.

Therapy with two therapists is just as good as therapy with one therapist.

And short term therapy (20 sessions and under) can produce positive results.

Summary:

In summary, we can say this. The research regarding the effectiveness of family therapy is complicated. However, generally speaking, research supports that family therapy, when conducted by people who know the theories and techniques well, can be helpful for a wide range of problems, although not for all problems. It would seem that overall, the different models of family therapy are equally valid and effective."

http://www.psychpage.com/family/library/family_research.html

https://www.utexas.edu/courses/franklin/Docs/September%205%20-%20The%20New%20Epistemology-%20History%20and%20Antecedents%20of%20Family%20Therapy%20Models/Pinsof&Wynne,%202000.pdf