... But I would so much like to have a proper diagnoses, that takes into account the meaning I attach to things, the state of the world, the peculiarities of modern information societies as well as my biological make-up. I'm afraid it'll be a long wait before we see anything close to it arising in medicinal science.
Nutritional deficiencies and lack of exercise is often a big contributor to anxiety and depression, and is generally overlooked by western (U.S. and European) medical and health experts.
Here in the U.S. most of the foods we buy in the stores or fast foods have almost no nutritional value, are loaded with sodium and almost everything has corn syrup and chemicals added that cause long term chronic illnesses such as diabetes and cancers as well as strokes and heart attacks. Not to mention GMO foods. The result is we have tens of millions with chronic illnesses.
If you add to that being out of shape, not regularly exercising can also lead to chronic health issues, but also emotional and brain function imbalances diminishing the chemical neurological functions. You might be surprised by how much energy is expending just thinking, even when one is not a deep thinker.
Consider, as an example, that we might get more tired studying a mechanics manual for an automobile, rather than physically working on the automobile.
Too often in this age, people seek an easy answer or remedy, to quick fix their issues, a pill cocktail, a diet, a surgical solution, or a vitamin supplement, but in reality, when dealing with health issues, it takes time for the imbalances or issues to manifest themselves into ailments, likewise, it will take time and effort to improve your health and regain a balance in body and brain functions.
In most instances nutritional choices are ours to make, as well as regularly exercising (even for people struggling with disabilities). A sound body supports a sound mind... Perhaps these things might be relevant to your quest to find solutions.