This is study from England which was published in 2016.  The authors investigated the impact of psychiatric comorbidities on length of stay (LoS) amongst 31,760 heart failurre patients admitted to hospitals in North England between 1st January 2000 and 31st March 2013.
Mean LoS in the absence of psychiatric comorbidities was 11.2 days. The presence of a psychiatric comorbidity increased LoS by 3.3 days. LoS was significantly longer in patients suffering from depression (3.4 days, p < 0.001), bipolar disorder (8.8 days, p < 0.001) and all types of dementia (4.2 days, p < 0.001).
1 Carter P, Reynolds J, Carter A, et al. The impact of psychiatric comorbidities on the length of hospital stay in patients with heart failure. Int J Cardiol 2016;207:292–6. doi:10.1016/j.ijcard.2016.01.132