BOSTON (AP) — A Massachusetts doctor has been sentenced to six months in federal prison for falsifying research into the effectiveness of some painkillers.

Scott Reuben, the former chief of the acute pain clinic at Baystate Medical Center in Springfield, was also sentenced on Thursday to three years of probation, ordered to pay a $5,000 fine and make restitution of about $362,000 to the companies that provided his research grants.

The 51-year-old anesthesiologist from Longmeadow pleaded guilty in February to health care fraud.

The hospital found that Reuben misrepresented findings in 21 studies dating to 1996. At least 13 of his studies published in professional journals had to be retracted.

His lawyers have said Reuben suffered from bipolar disorder.