Is it permissible for parents to prevent their son from marrying a specific girl for psychological reasons, and what are the consequences of that, such as the son refraining from marriage or secretly marrying, and does Islam grant the right to choose a partner to a mature, sane adult?

It is not permissible for a son to marry a woman whom his parents object to, unless their objection is without a valid reason, and the son would suffer religiously or worldly harm if he were to abandon marrying the woman he desires. In this case, it is permissible for him to do so, and his marriage would then be valid.

It is not permissible for a father to prevent his son from marrying whom he wishes, or to compel him to marry someone he does not love, because an adult, mature man is not under anyone's guardianship in matters of marriage.