BOSTON -- A state senator accused in a string of sexual assaults may use a diagnosis of bipolar disorder as his defense at trial, sources close to the senator told the Boston Herald.

Sen. James Marzilli, 58, D-Arlington, is receiving treatment at a psychiatric facility for the disorder that causes wild mood swings, the newspaper reported.

“It can affect all aspects of someone’s behavior,” Dr. Roy Perlis, a psychiatrist at Massachusetts General Hospital, told the Herald. “A person may make advances that they would ordinarily not make or say things that are inappropriate. It can wreck relationships. It can wreck their employment.”

Sources told the Herald that Marzilli is being treated for hypomania, which is caused by bipolar disorder. Hypomania can cause loss of sleep, racing thoughts and inability to control behavior, according to psychiatrists.

Marzilli checked into the hospital in June after he was accused of lewd acts and making lewd comments to women in Lowell.

He was charged with disorderly conduct, resisting arrest, attempting to commit a crime, assault and battery and obstruction of justice.

It is unclear how the senator’s ongoing treatment could affect his legal case.