|The bullfighter (deceased) @Manet @Wikipedia|
So, take several groups of adult participants who were admitted "for an acute episode of DSM-IV nonaffective psychosis..., affective psychosis... or alcohol detoxification" and compare with an asymptomatic control group. Analyse for the presence of laboratory-confirmed UTI and voilà, after controlling for potentially confounding variables "UTI was almost 11 times more likely in subjects with nonaffective psychosis than controls". That and the fact that in cases of affective psychosis (major depressive disorder with psychotic features) the odds ratio for a UTI was up at nearly 9x more likely.
Coincidence I hear you cry. Well it certainly could be. But the data is strengthened by the fact that this is not the first time that this association has cropped us as per another paper by the same authors  covered by Dr Emily Deans over at Evolutionary Psychiatry. The fact that UTIs show more than a passing connection to behavioural and psychiatric features as per the evidence looking at delerium  for example should also be mentioned.
As to the reason for the association, well to quote from the NHS Choices entry on the causes of UTI: "Most urinary tract infections (UTIs) are caused by bacteria that live in the digestive system". The process of how said bacteria get from bowel to erm, nether regions is slightly more complex and could be related to hygiene practices (remember: wipe from front to back after going to the toilet) or other behaviours. One can't exclude the possibility that where psychosis occurs, such factors might come into play.
That being said, I'm also quite interested in whether there may be other reasons for the association made by Graham et al. Readers might remember back to a post I wrote recently on bacterial infections and behaviour (see here) part of which mentioned the paper by Blomström and colleagues  on bacterial infections requiring hospital admission and risk of later nonaffective psychosis. Given the focus on childhood in that paper, which I assume to some degree negates the possibility of sexual activity or kidney stones or a urinary catheter as being a primary cause of a bacterial infection like a UTI, one wonders if there may be something more biologically fundamental to account for the association.
Indeed, a quick trawl through the collected research literature in this area reveals some potentially relevant findings in relation, for example, to the development of psychosis after a kidney transplant  (open-access) and how this particular patient developed anti-NMDAR encephalitis (see here). I'm wondering whether immune suppression may be a contributing factor to the UTI - psychosis correlation, as per data on the infections favoured following something like organ transplant  and the degree to which UTIs are involved. That being said, a role for the immune system in psychosis is a mighty complicated subject as per other posts on this blog (see here and see here) and short of suggesting that immune function might be involved in the link with elevated rates of UTIs in cases, there's few comprehensive answers to account for the association at the current time.
Still it is an interesting area of work, also raising the question: does the treatment of UTIs have any effect on presented psychosis symptoms? Bearing in mind, the evidence so far seems a little bit contrary... [Finish post with head scratch and confused look].
Music to close. Pavement and Cut Your Hair...
 Graham KL. et al. Urinary tract infections in acute psychosis. J Clin Psychiatry. 2014. Jan 21. [Epub ahead of print]
 Miller BJ. et al. A prevalence study of urinary tract infections in acute relapse of schizophrenia. J Clin Psychiatry. 2013 Mar;74(3):271-7.
 Lin RY. et al. Clinical associations of delirium in hospitalized adult patients and the role of on admission presentation. Int J Geriatr Psychiatry. 2010 Oct;25(10):1022-9.
 Blomström A. et al. Hospital Admission With Infection During Childhood and Risk for Psychotic Illness--A Population-based Cohort Study. Schizophr Bull. 2013 Dec 23.
 Zhao CZ. et al. Clinical reasoning: agitation and psychosis in a patient after renal transplantation. Neurology. 2012 Jul 31;79(5):e41-4.
 Galindo Sacristán P. et al. Predictive factors of infection in the first year after kidney transplantation. Transplant Proc. 2013 Dec;45(10):3620-3.
Graham KL, Carson CM, Ezeoke A, Buckley PF, & Miller BJ (2014). Urinary tract infections in acute psychosis. The Journal of clinical psychiatry PMID: 24499998