Hyponatremia, or water intoxication, is the result of over-ingestion of water, and can cause death. 
The three groups of people most likely to die from hyponatremia are military in the field, athletes in competition, and schizophrenics. 

It appears that the fear of dehydration causes military members and athletes to overhydrate, 
and overhydration has symptoms similar to dehydration, which induces further overhydration.
And apparently, some schizophrenics overhydrate to commit suicide. 
Urine analysis test strips are available to test hydration levels. 
Do military squads have these test strips to care for their personnel? 

https://www.medicalnewstoday.com/articles/318619.php https://www.outsideonline.com/2148776/new-rules-hydration 

Overhydration and Mental Illness 

Hungry, homeless people, including veterans, fill their bellies with whatever they can find. This is what hungry people do. 
Dirt-eaters existed in Appalachia. https://www.ncpedia.org/dirt-eaters. 
Water is another way of filling an empty belly.
And anorectics under treatment may over-consume water to hit weight targets, then fall into overhydration.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3136024/ talks about psychiatric issues stemming from water dysregulation. 
Overhydration can cause mental illness. 
This website infers that some mental health issues can be improved with simple water intake management. 

So, should urine analysis be a first step in veteran mental health and suicide intervention? 
And what about testing apparently mentally-ill people as they are booked into jail? A simple test strip…      

Eric J. Rose