Which of the following can be considered a method of psychological duress in custody matters?

Using children as messengers can indeed be considered a method of psychological duress in custody matters because it places an undue emotional burden and stress on the children involved. When children are used as intermediaries in communication between parents, it can create situations where they feel pressured to take sides or relay messages that are inappropriate or distressing. This can harm their emotional well-being and can disrupt their sense of security and loyalty.

In custody cases, the best interests of the child are paramount, and involving children in adult conflicts undermines that principle. It can lead to conflict escalation and can adversely affect the children's perceptions of their parents and their relationships with both parents.

Other options, while relevant in a custody context, do not directly impose psychological strain on children in the same way that using them as messengers does. This makes the correct choice particularly relevant in discussions about the welfare of children in divorce or custody disputes.