Dr. Renee Roy started treating Magnotta in November 2012, almost six months after he was charged in the slaying and dismemberment of Jun Lin in Montreal.
Magnotta has admitted to killing the 33-year-old Chinese engineering student, but has pleaded not guilty by way of mental disorder.
The first time Roy met with Magnotta, she knew he had past mental health problems and had been diagnosed as a paranoid schizophrenic.
Roy said Magnotta was heavily medicated as doctors tried to determine the right dosage to help with anxiety, sleep issues and the schizophrenia.
The medication is one reason his weight has ballooned. He was roughly 130 pounds when arrested and now weighs about 200 pounds. He would also eat quite poorly, with ice cream and pizza among his favourites.
Roy testified that once Magnotta began taking the medications, his hallucinations and delusions became less intense. He would, however, spend a lot of time sleeping.
During those first meetings, Roy noted that Magnotta expressed concerns about his impending legal case, that jail staff would harm him and that other inmates were spying on him at the behest of police.
"He doesn't show a lot of emotion," Roy wrote early on in their time together. "He speaks in a very neutral tone."
Magnotta rarely exhibited any emotion. One exception was just before Christmas 2012 when a nun who'd been counselling him died of cancer. The nun was on the phone with Magnotta when she died.
He was also very happy to hear from his mother, sister and grandmother in February 2013, according to Roy.
"They are important people to him, in particular his grandmother," she said. "It had been months since he'd heard from them."
Magnotta no longer has any contact with that side of his family, Roy added.
Movie references surfaced often with Magnotta and he told Roy he would hear Monroe's voice on a regular basis.
In February 2013, Roy noted Magnotta was having trouble sleeping and that he had dreamt he was being chased by Jason, the hockey-mask-wearing, machete-wielding lead character from the "Friday the 13th" movies.
The psychiatrist also offered an explanation for a well-publicized collapse Magnotta had during his preliminary hearing in 2013.
A secondary effect of one of the medications was a drop in blood pressure and a quick movement of his head may have triggered a blackout, she said.
The jury also heard Magnotta tried to enrol in correspondence classes around April 2013, but was forced to abandon his French studies because he couldn't concentrate.
Lin's name only emerged twice during their meetings, Roy said. Magnotta was moved into a new cell and was upset by graffiti that referred to Lin and the murder charges. At one point, Magnotta wanted to write a letter to Lin's mother to apologize, but Roy suggested he speak to his lawyer.
Earlier on Monday, a family doctor who saw Magnotta for six years in Toronto told the court his patient was convinced in 2005 that he was being stalked and that voices in his head told him he walked like an ape.
Dr. Allan Tan testified that a psychiatrist had diagnosed the accused as manic depressive and mildly schizophrenic even before Tan began seeing him in 2003.
Magnotta was also taking several psychotropic medications, had been hospitalized three times for manic depression and was routinely being seen by a psychiatrist, said Tan, who was Magnotta's doctor until 2009.
Tan testified it was in 2004 when he first noted in his files that Magnotta said he was hearing voices.
In March 2005, Magnotta told Tan that people were taking pictures of him and posting them online in an attempt to ruin his modelling career.
Tan testified the psychotic episodes he saw were rare.
"Most of the time he was functional," he said. "There were times he had mental problems."
Tan said he knew Magnotta first as Eric Newman — the accused's birth name. In 2006, he changed his name to Luka Magnotta and told the doctor he did so because he thought he was being followed.
Magnotta faces four charges in addition to the premeditated murder of Lin: criminally harassing Prime Minister Stephen Harper and other members of Parliament; mailing obscene and indecent material; committing an indignity to a body; and publishing obscene materials.
Follow @sidhartha_b on Twitter.