The parents attention towards their children especially as young adults really matter a lot. Depending on how the parents relate to them they may or may not be able to relate somethings with them concerning what they may be going through.
As parents it's not all the time we wait for the children to approach them and express to them how they are feeling, there are times you need to be the one to inquire by asking them if everything is alright and paying close observation to them.
Parents need to come to the point that they make their children aware that they can confide in them about anything. A child is not supposed to die in silence if he or she has a working relationship with the parents. One of the factors that may discourage the child from opening to the parents about a particular thing is if the parents are not cooperative with each other. Having parents would fight a lot could be enough trauma already for the child.
What someone who is going through depression needs is encouragement and extension of love and care. A child needs to feel loved first at home before outside. Parents should ensure to engage in quality bonding with their children. Little things like going on outings together, praying together and even eating from the same table can go along way. This keeps children from feeling isolated which is a key factor of depression.