Always use sulfate-free shampoo. Much better for the hair. I have long hair, and regular shampoo really dries it out.
Anyway, I have worked in health-care for 15 years, before I was diagnosed with BP and became so sick that I could not work much at all. One thing that is a sign of depression is poor ADL(Activities of Daily Living). Having a hard time with personal hygiene, among other things. And showers are very often on top of that list. Taking a shower is made up of a lot of smaller tasks, that put together easily becomes overwhelming. And some decision-making is thrown in there also. (Do I wash my hair, and if I do, then that includes a bit of extra work also - extra maintenance post-shower...). And of course, in addition to an overwhelming sequence of small tasks, comes the various phobias and anxieties that comes along with standing naked in a small cubicle with water falling down on your body. Poor body-image is also a factor that makes taking a shower unpleasant. For me, I sometimes just take a sponge-bath, if the whole shower-thing becomes too much of an undertaking. Better to do that than to spend all morning obsessing about showering.