In medical school depression was not a difficult subject. Today when I talk to my colleagues about depression we agree that it is a difficult diagnosis. In itself the diagnosis is a quite simple syndrome of x symptoms for y amount of time. But when you talk to persons presenting depression-like symptoms it is often difficult to make sure that it is a depression and thus
- is global (affects all parts of life)
- has no major fluctuations in the past weeks (many hours or days of feeling happy/normal)
- the quality of the feeling is depressed (feelings are difficult to describe)
- low reactivity (e.g. low energy after to much work, more often burnout than depression).
Then you also have to distinguish depression from other mental disorders e.g. anxiety disorders.
You can find the ICD-10 green book (research criteria) and blue book (clinical) for diagnosis of mental disorders on google for free. It is a bit heavy reading but then you go straight to the source of the clarification. ICD-10 is used in most of the world. The US uses the DSM-5 made by the APA which is similar but costs a lot of money. The library should have a copy.
Concerning SSRI the consensus is that they work. Not a wonder drug but it helps many people with depression (and anxiety). The biological source(s) of depression has not been fully established but placebo and randomized clinical trials testing SSRIs on 1000s of participants have found clinical effect. Much like e.g. migraine that is also not fully understood but some drugs have been found to have clinical effect. A minority of professionals argues that SSRIs don't work or side affects are worse than the antidepressant effect.
The major problem is that many people take it as the only treatment because it is cheap and convenient. Guidelines recommend a more holistic approach including some form of psychotherapy. See e.g. NICE guideline from the UK for depression that recommends SSRI (not always for less severe depressions) and other treatments:
https://www.guidelines.co.uk/mental-hea ... 26.article
Books
CBT you can try out alone as the therapist more or less follows a manual that you can find online. A good place to start could be the Beck Institute. I have heard good things about them but I'm not specialized in CBT:
https://beckinstitute.org/cbt-resources ... dividuals/
I work with the psychoanalytic/psychodynamic approach.
irvin Yalom has written great novels for layman about the approach e.g. "Lying on the couch".
Glen Gabbard's "Psychodynamic psychiatry in clinical practice" (any edition will do) was for me the best intro to theory and clincal work. He gives a brief intro to ego psychology, object relations theory, self psychology and attachment theory, and then covers treatment of all major disorders.
Bruce Fink's "Fundamentals of Psychoanalytic Technique: A Lacanian Approach for Practitioners" was fpr me the best intro to lacanian psychoanalysis. The book describes how Lacan developed Freud's understanding of the unconsciuos and added linguistic theory.
Both books have many examples and short patient notes/vignettes. I think that the books can give some insight to layman, esspecially on how our past intereferes with the present and that many processes are unconscious. But I'm not sure that it will create as much change doing it yourself compared to CBT that is much more tangible and only concerns conscious problems.