Hi. In this case you can go through some outcome measures using for depression e.g..  Beck which implemented in hospital patients. 

Hi,

You might find this paper relevant too.

Regards

Article No further research needed: Abandoning the Hospital and Anxi...

Hi Bruno, 

Hospital Anxiety and Depression Scale

Interpretability: The results are easy to interpret with higher scores on each individual scale or the entire scale indicating greater anxiety, depression or mood disorders.

You have your sample and based on that you get a mean. Look then at those who have the lowest third and the highest third of the scores. Calculate differences and do correlations with other indicators. I did so with my BDI scores in my hysterectomy-vasectomy papers

http://www.abiebr.com/node/410

These scales measure recent symptoms of depression and anxiety. The scales are aimed at identifying the current state (past week usually), which means they are not equivalent to a diagnosis of a depressive or anxiety disorder, since such disorders are defined by both current and especially past episodes. As for how many points are clinically significant, there is no single number but a 1-2 point change is well within the normal daily fluctuation, whereas a 10 point change would be unusual, so somewhere between 2 and 10 would usually be clinically significant, depending on the context.

Be careful. For a start, the depression and anxiety sub scales are highly correlated, and the anxiety sub scale is a better measure of depression than anxiety– it correlates poorly with clinical anxiety diagnoses, but very well with depressive diagnosis. 

The studies that have been done validating the HADS against clinical diagnosis suffer from the use of multiple, ad-hoc cutoffs. Cosco reviewed 50 studies of the structure of the HADS and concluded that 

The heterogeneous results of the current review suggest that the latent structure of the HADS is unclear, and dependent on statistical methods invoked. While the HADS has been shown to be an effective measure of emotional distress, its inability to consistently differentiate between the constructs of anxiety and depression means that its use needs to be targeted to more general measurement of distress.

Coyne and van Sonderen go much further – it's a paper that you simply have to read! They note, among other things,

ambiguity in the language of items, particularly the use of British colloquialisms aggravates this problem in the HADS literature and introduces differences in performance of the HADS across lan- guages and cultures [2] that should discourage uncritical integration of cross-cultural studies into systematic reviews and meta-analyses. Strangely, reviewers keep stumbling upon evidence pointing to these issues, sometimes noting them and usually not. They inevitably continue to recommend the HADS as a screening instrument or major depression and anxiety, although sometimes with the suggestion that the HADS needs to be recalibrated in new samples [7], which is no small task because such re-calibrations need replication that is rarely done.

Finally, my wife and I did some work on the HADS. Tested against clinical interview, it has a really remarkable false-negative rate. So beware. 

Cosco, T.D. et al., 2011. Latent structure of the Hospital Anxiety And Depression Scale: A 10-year systematic review. Journal of psychosomatic research, pp.1–5.

Coyne, J.C. & van Sonderen, E., 2012. No further research needed: Abandoning the Hospital and Anxiety Depression Scale. Journal of psychosomatic research, pp.1–2.

Golden, J., Conroy, R.M. & O'Dwyer, A.M., 2007. Reliability and validity of the Hospital Anxiety and Depression Scale and the Beck Depression Inventory (Full and FastScreen scales) in detecting depression in persons with hepatitis C. Journal of Affective Disorders, 100(1-3), pp.265–269.

Thanks everyone! Very helpful

Further to above, can the instrument still be scored with missing answers?