How do I orient myself to the literature concerning a research topic and not be overwhelmed?
Start with well-written review papers. These are designed to do exactly what you ask: to orient a reader to the state of knowledge in some field. If you are working on something multidisciplinary you may need a separate orientation for each discipline if there isn't a good review that already makes the connection for you.
Then, once you are oriented, you can start to dig. Try to discipline yourself towards pursuing a specific goal in your literature search. When you find offshoots, label them as future places to dig but don't start excavating them quite yet.
Other than that, try to stay organized. Organize your thoughts by writing down what you are learning, make concept maps if they help you, or start organizing references into nested bulleted lists. Be open to reorganizing as things develop.

I want to add an addendum concerning your specific field of research. Published science in biology and medicine, and even more so in areas related to mental health/psychiatry/counseling, may contain a lot of conflicting information. These fields deal with some of the most complex systems humans know of, and our core knowledgebase is extremely lacking. If you're used to reading textbook descriptions of &quot;how things are&quot;, the actual academic literature is by comparison extraordinarily muddy (this is true of all fields, no doubt, but I think especially the ones I've mentioned). It may help to know to accept this, and to not treat any one paper as Truth. There are competing models and competing hypotheses and competing approaches to treatment because none have yet &quot;won&quot;.
Adding  from a comment: if you are wondering how to find review papers...
There are some journals that only contain reviews. Some of these are good journals (and since reviews tend to get cited a lot, you can often discover them by their very high impact factors), some are not (these will tend not to be cited much). Some indexes, like PubMed, allow you to filter for only reviews (I don't know how accurate these filters are). Otherwise, adding &quot;review&quot; to a search string will help. You won't get all reviews, but many of the top results will be.