The England batsman has not played this season and there is no timeline over his return to action, though he has resumed training
Gary Ballance, the Yorkshire and England batsman, has been fighting anxiety and stress caused by the COVID-19 lockdown.
The 30-year-old has previously dealt with periods of apprehension and those feelings have returned in recent months.
Ballance has also been battling with symptoms of coronavirus, though has twice tested negative for the disease.
Yorkshire have been without Ballance this season and despite recently returning to training there is no indication he is ready to return to competitive action.
In a statement to the Yorkshire Post, Yorkshire said: "Gary is currently managing some heightened feelings of anxiety and stress following a long period of isolation due to the Covid-19 lockdown, his own recent viral illness and other personal factors. The post-viral symptoms have affected his physical preparation for this shortened cricket season.
"He is currently unavailable for selection and we are unable to put any timescales on his return to playing at this time.
"However, Gary has increased his training volumes over the last week and is working hard both in the nets and on his general fitness.

Gary Ballance has four Test centuries for England
"Gary’s health and well-being remains our priority and the club and medical staff will continue to work closely with Gary to support his return to playing as soon as possible.
"The club requests that Gary’s privacy in this matter is respected to allow him to focus on his return to cricket.
"The club will make a further announcement when Gary is ready to return to action."
The Zimbabwean played 23 Tests and 16 one-day internationals for England and has a first-class average of 47.40.
In 117 FC outings for Yorkshire he has scored 7,913 runs with 26 centuries and a best of 203. A former skipper at Headingley, he remains a key figure at the club; only Dom Sibley notched more runs in County Championship Division One last season.
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