Nottingham Crown Court was told that the attack carried out by Kamil Dantes was so ferocious that he snapped the blade of one knife as it was embedded in his mother’s skull.
The 29-year-old then calmly went back downstairs to get another knife before returning to the bedroom and killing his disabled father.
Leszek and Malgorzata Dantes, both aged 54, were found dead at their home in Hardwick Road East, Worksop, on Monday 21st April, 2014.
Dantes had called the police at 6.55am that morning and said that he had killed two people and needed an ambulance because he had injured his hands.
Medical experts said Dantes had a history of delusions and showed symptoms associated with schizophrenia that stretched back a number of years and for which he had been receiving treatment.
Dantes even admitted using cannabis every day, and the night before the killings, he said he had taken amphetamine.
He had always denied murder, but accepted manslaughter on the grounds of diminished responsibility, which the crown prosecution service accepted.
The judge, Mr Justice Haddon-Cave said: “Your exact motivation may never be known, but what is known is that you subjected them to the most ferocious attack.
“The police saw the most terrible scene of death.
“One can only imagine the horror that your mother and father felt at being attacked by their son.”
The hearing was told how the Polish-born Dantes had move to Britain when he 22, and had worked shifts at a sandwich factory along with his parents.
But Dantes’ mental health began to deteriorate and even once told doctors that his parents had died years ago and the two people he lived with were imposters and were wearing ‘skin masks’ of his parents, comparing it to the John Travolta movie ‘Face-Off’.
He later retracted the statement saying he been ‘watching too many films’.
He was put on medication to control his behaviour and appeared to be improving.
Despite regular visits to doctors in the months leading up to the attack, he hid the fact he was still smoking cannabis regularly.
The night before he killed his parents, he had been unable to sleep after taking amphetamine.
In the early hours he went into the kitchen and took a knife, concealing it before heading up to his parents’ bedroom.
He knocked on the door and when his mother answered, he stabbed her between 20 and 30 times, breaking the knife.
He then fetched another knife and attacked his father who was in bed, stabbing him 20 times.
His father had been left disabled by a stroke in 2013 and could do little to defend himself, although stab wounds to both parents’ hands showed they had tried put up some resistance.
Mr Justice Haddon-Cave said: “It’s clear you were harbouring dark thoughts for killing your parents for some time.
“You committed the most serious of offences, you attacked them in their bedroom, you killed one parent in the presence and sight of the other.
“You intended to kill and used brutal force.
“What is very clear from your deteriorating mental health have much to do with your drug abuse, and in particular your cannabis habit.
“It’s yet another example of the dangers of cannabis abuse and it’s ability to induce psychotic behaviour in young men.
“In this case the consequences were terrible and tragic.
“I’m satisfied that you remain an ever-present serious threat to others, including members of your family. You are likely to attack them because of your paranoid and persecutory beliefs.”
He ordered that Dantes spend at least 17 years and 354 days in custody at Rampton Secure Hospital.
He had been given credit for his early guilty pleas and time already spent on remand.