The 23-year-old has not played for the Baggies since September, but is eager to return for Tony Pulis's side.
Berhaino saw West Brom reject a transfer deadline day bid from Spurs before the start of last season, and signals that as the start of the lowest point in his career.
"This last year has been the most difficult of my career and it has left me short of the form and fitness required for the Premier League," Berahino told the club's official website.
"I have never been a player who lacked confidence or a belief in himself but that has been where I have found myself and it has hit me hard.
"It has left me feeling depressed and struggling for focus which has made it even more difficult to regain full fitness."
The former England Under-21 international was the subject of a transfer bid from Spurs after hitting 20 goals in the 2014-15 season, but netted just seven goals in all competitions last season as he struggled to recreate that form.
However, he is looking forward to getting his career back on track after spending time building his fitness in France.
"I have had a good, constructive talk with Tony and the senior management and we all agree this is the best way forward for me," Berahino said.
"“I want to thank my team-mates who have been willing me on and providing positive support. I want nothing more than to earn my place alongside them and get back on the pitch scoring again."