An inquest heard Mr Hornsby died as a result of drug intoxication which caused him to fall into the river and drown.
David Roberts, senior coroner for Cumbria, concluded it was accidental death.
A post-mortem found the medical cause of death was drowning with drug use as a contributing factor.
Mr Hornsby, who had a history of drug use, had taken a mixture of illicit and therapeutic drugs.
Mr Roberts said the drugs had affected Mr Hornsby's ability to think straight and he had fallen down a steep and quite dangerous bank near Egremont Rugby Club.
Ian Rumney, who is married to Mr Hornsby's mother Patricia, said his stepson had visited the couple in the early hours of December 24 and he had seemed agitated and under the influence of drugs.
His mother had asked him to call when he returned to his Beck Green home but when this didn't occur Mr Rumney went to the house to check on him at around 3am.
When he arrived, he found the front door open and the oven on.
Mr Rumney continued to check the house regularly before informing police just after 9am.
Mr Hornsby was eventually found by Wasdale Mountain Rescue Team.
The 32-year-old had attended Montreal and Ehenside schools, and had also spent time living in Millom.
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