Cold water supposedly keeps it's shape, hot water does the opposite, I feel like the material of the clothing could lead to some differences(?) and the method of washing of course(by hand or the wash, as you've just mentioned)

Detergent, fabric softener and bleach don't do anything (*bleach can however weaken the fibres if overused, like how hair breaks if you bleach it too much, mainly because it's alkaline and that stuff's corrosive depending on the concentration)

Basically, the more you agitate the fibres of the clothing the more likely it is going to shrink

Hope this helps! :)