All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Islam encouraged taking the initiative to marry at an early age because there are many benefits in early marriage, for more benefit, please refer to Fataawa 91351 and 88277.
As regards delaying the marriage, then this is not encouraged because this leads to missing those benefits which are attained by early marriage, and in general it has negative effects. Among these negative effects is that it may lead to the spread of Zina (fornication or adultery), increase of spinsterhood and spread of psychological and behavioral disorders.
For more benefit on the medical point of view in this field, you may consult specialist doctors.
Allaah Knows best.