I am conducting a systematic review and have run all my database searches (PubMed, Embase, CINAHL, Cochrane CENTRAL etc.) I am now in the process of searching for grey literature, which there seems to be an endless ocean off.

The problem is that I find it difficult to locate a large number of relevant conference proceedings. E.g. I have decided to check conferences and symposia run by e.g. the Royal College of Psychiatrists, the American Academy of Addiction Psychiatry etc., but I struggle finding out about their conferences. The RCP website has a small list of their annual meetings run since 2007, but that's it. I am pretty sure they have already had conferences way before 2007, but cannot find any information on them on their website. The same goes for other organisations in the field of my research - I'm lucky if their websites have any sections containing any conference proceedings at all.

Does anyone have any advice about finding such proceedings in their entirety, i.e. all of them for every year? Otherwise I will probably have to resort to contacting the organisations directly ...

I've also tried to find conference proceedings before and I've concluded they probably weren't digitised and uploaded in the early days so that's why only later versions are online.

Sometimes I've found random articles online, but I think this is where authors have scanned their article in the proceedings and uploaded them.

I would contact the organisations directly yeah, maybe they've got extra copies they can send or scan.