Several German newspapers broke the story on Friday and Bayern Munich coach Ottmar Hitzfeld confirmed the details later in the day.
"He is undergoing treatment," said Hitzfeld. "We had hoped that his great performances on the pitch would help him through it.
"It is a setback for us all, and I assume he won't be playing again until the New Year."
Earlier in the week, Bayern announced that Deisler was suffering from flu and would be unavailable for Saturday's local derby against 1860 Munich.
The German international star has been plagued by injuries throughout his career at Monchengladbach, Hertha Berlin and Bayern, and is known to not enjoy the Bundesliga media limelight.
This, coupled with concern over the health of his pregnant girlfriend, are said to be the causes of his illness.
"Of course he is under a lot of pressure. Players react to pressure in different ways and one shouldn't underestimate that," Hitzfeld added.
Deisler was the brightest German player of his generation and everybody will be hoping he can rediscover his best form.
