When people are positively convinced a treatment will work in real world conditions they are more likely to keep to the treatment. If patients are not convinced the treatment will work, they will slack on the treatment. If the slackers had pressure from someone they trust they were more likely to stick to the treatment.
Positive thinkers stick to treatment http://www.sciencealert.com.au/news/20081107-17648-2.html
“We found a person’s beliefs about the treatment’s effectiveness, their confidence in sticking to the treatment, and their understanding of the condition’s health risks, were more important than the severity of the disease.”