I consider the paper by Pedersen & Saltin  (open-access available here) to be pretty good scientific value insofar as their providing the reader "with the up-to-date evidence-based basis for prescribing exercise as medicine in the treatment of 26 different diseases."
Including various psychiatric labels - "depression, anxiety, stress, schizophrenia" - as an addition to their previous review in this area , the authors have quite comprehensively trawled through the available peer-reviewed literature to arrive at a summary of what the research evidence suggests, the possible mechanism(s) of action of exercise use and where discussed, the type of training that might best fit with the label.
I'd prefer not to dwell too long on the findings in their entirety because there are quite a lot of them. Given however that topics such as depression, anxiety and schizophrenia have been discussed on this blog before with physical activity and exercise in mind (see here and see here for example) I thought it might be useful to mention a few points bearing in mind my blogging caveats about not giving anything that looks, sounds or smells like clinical advice.
Depression: "some, but modest evidence of a positive effect of physical training on depression symptoms." Bearing in mind that the label 'depression' covers quite a bit of diagnostic ground, specific recommendations about a best type of exercise were not made as were details on how exercise might specifically act upon cases of depression. This last point has however been explored in other research . The authors did however suggest that: "more sessions have a larger effect on depression score than a smaller number of sessions" and "resistance and mixed training may be more effective than aerobic training."
Anxiety: again, bearing in mind that anxiety comes in various different guises, there was "some, but limited knowledge about the effects of physical activity as a treatment for anxiety." Anxiety when coincidental to various chronic diseases such as cardiovascular disease or chronic obstructive pulmonary disease (COPD) did seem to be positively affected by physical activity based on some meta-analyses. The authors were able to be a little more specific in the potential best types of exercise in the context of anxiety such that "individualised" and exercise under supervision might be a useful start. Small group training was also suggested, initially starting with "low-intensity aerobic physical activity" including walking, swimming and cycling.
Schizophrenia: accepting that the physical health of those diagnosed with schizophrenia has been an area crying out for further research, the authors highlight several pertinent issues when it comes to physical activity and schizophrenia in relation to the issue of comorbidity ("People with schizophrenia often have accompanying symptoms, such as anxiety and stress") and the possible impact that certain pharmacotherapy used for schizophrenia might have on factors affecting/affected by physical activity and exercise. They do however report that exercise does seem to impact on the presentation of schizophrenia: "Psychiatric symptoms were significantly reduced by interventions using around 90 min of moderate-to-vigorous exercise per week. This amount of exercise was also reported to improve functioning, co-morbid disorders, and cognition." Further: "It is important for the training to take into account the individual situation of the person in terms of physical environment, a recognizable structure and level of social participation" with a recommendation "to start with low-intensity aerobic exercise and gradually increase to moderate intensity, with a gradual increase in duration."
There is a need to build upon such reviews and further zoom in on what might be the optimal exercise pattern for labels and indeed, for individual people. Set within the context of other health promoting regimes (affecting diet, smoking and drinking habits and other aspects of health for example) and without coming across as too 'nanny state', the authors conclude: "it is now time that the health systems create the necessary infrastructure to ensure that supervised exercise can be prescribed as medicine."
To close, yes yet another Force Awakens trailer as this week all is revealed...
 Pedersen BK. & Saltin B. Exercise as medicine - evidence for prescribing exercise as therapy in 26 different chronic diseases. Scand J Med Sci Sports. 2015 Dec;25 Suppl 3:1-72.
 Pedersen BK. & Saltin B. Evidence for prescribing exercise as therapy in chronic disease. Scand J Med Sci Sports. 2006 Feb;16 Suppl 1:3-63.
 Schuch FB. et al. Neurobiological effects of exercise on Major Depressive Disorder: A systematic review. Neuroscience & Biobehavioral Reviews. 2015. 2 Dec.
Pedersen BK, & Saltin B (2015). Exercise as medicine - evidence for prescribing exercise as therapy in 26 different chronic diseases. Scandinavian journal of medicine & science in sports, 25 Suppl 3, 1-72 PMID: 26606383