By jnana yoga one can achieve meditative strength and wisdom as well.
In Jnana yoga, a person derives his knowledge and his awareness through meditation. Meditation will help the person find rational answers to all questions that are in nature, body and mind. With the help of Janna yoga, one can realize knowledge about atman that is self and Brahman that is ultimate self by that one can achieve moksha which is the ultimate aim of person.
Janna yoga is contraindicated for mentally ill person.