Samuel Harrison died at his home on Barlborough Road, Clowne, on February 11.
He was only 26-years-old.
An inquest into the fork lift truck driver's tragic death took place at Chesterfield coroners' court on Wednesday.
Coroner Peter Nieto said: "On the post-mortem evidence, namely toxicology evidence, Mr Harrison died as a result of taking a quantity of heroin within the range known as capable of causing death.
"Of note Mr Harrison was not known to have used heroin previously and he would therefore have had low tolerance to a relatively high dose.
"Mr Harrison was recognised to be experiencing low mood prior to his death and he was very preoccupied over the breakdown of his relationship with his partner.
"He had a history of self-harm and had self-harmed about a week before his death.
"On the balance of probabilities, Mr Harrison undertook a deliberate act in taking heroin and by that act had intended to take his own life.
"On particular relevance, Mr Harrison left leters to family and close friends which read as suicide notes."
Mr Nieto concluded that Mr Harrison died by suicide.
He recorded the medical cause of death as fatal heroin ingestion and mental health issues.
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