Yes, this can be true. It is dependent on many things:
Your hormonal balances
the influences of your surroundings and surrounding people
Other factors (i.e. relationships, health, religion)
As I am sure you are aware from about the age of 13 most people go through stages of hormonal development. The final and many beleive the most important stage occurs between the age of 18 and 22, this is when many beleive that 'real maturity' occurs. As the hormones balance and stabalise. This seems to occur earlier in females, therefore the changes in attitude and interests can occur earlier than in males.
This change in hormones and possible greater knowledge on the world or increasing amount of adult experiences can change your view on the world, and thus what you enjoy doing.
I personally beleive that it happens in everyone. Some on a greater scale and it is a mixture of this hormonal change with changes in your enviroment.
So....in summary. Yes many people do mentally change between 18 and 22.
(sorry for it being so long....!)