We have a body and a soul. You can't validate someone's thoughts and feelings. You do the best you can to relieve distress. If you insist on a biological correlate before you help, you leave a lot to suffer. So that's where education, lots of experience and wisdom comes in. Stress, or distress, can be assessed, as best as we can at the mo, using a combination of measures, including my favourite, the Perceived Stress scale, plus four cortisol measures per day (saliva) and asking people about how they feel. If you compare patients with high scores for stress with those with low stress, you can get an idea what is linked to stress and what is not. You can do a test, e.g. measure cortisol before and after an exam, or follow carers of people with dementia over years. Statisticians can partial out the effect of stress. We've obtained quite a lot of info on the effects of distress that way. Abuse during stress is associated with increases in certain cytokines years later (Danese and others). We don't know why, but that kind of finding has been replicated. Sex abuse is not good for your health. Ergo, Heims' findings. Did the stress from the abuse mess of the immune system? Jason has a kindling theory. But stress does have a pro-inflammatory effect. If you want pure science, you study maths. When feelings are involved, you have to look at things in a number of different ways and hypothesize and test. Depression can shrink the hippocampus, stress can decrease grey matter volume (and CBT can increase it), so neuroscience is interesting. But there's always the possibility that the reduction in grey matter volume is the result of a disease process. If you don't remove the individuals with stress, you can't interpret the findings. Scanners are a great help. Costa et al showed that ME is linked to hypoperfusion of the brain stem and ME plus depression to almost normal blood flow (as depression itself increases blood flow). So you need pure groups. Acute stress is linked to high levels of am cortisol; chronic stress/burnout to low levels. but not in everyone as different patients cope with stressors in different ways and at diffferent times. That's why five years plus one to get Europsy certification is very basic. As we are body and soul, I can't see many disorders that have one physical cause (exceptions include norovirus and salmonella). With stomach ulcers, there's H pylori and yet, stress also plays a role. Heart disease is a result of many factors, as is breast cancer. Severe distress can result in a relapse in someone who has already had breast cancer. It's all very complicated. Short answer: no, you try and use reliable measures and so on but some aren't as bothered as I am. I am a nitpicker. There's a lot I don't know. I do know that kindness is a great antidepressant.