Arthur Cave, 15, was found with multiple injuries on the underpass of Ovingdean Gap in July. He died later at the Royal Sussex County Hospital.
Sussex Police said his death was not suspicious, and the coroner ruled it was "accidental".
Nick Cave, 58, is an Australian songwriter and is best known as lead singer of Nick Cave and the Bad Seeds.
Mr Cave and his wife Susie Bick are at the hearing which is being held in front of Brighton senior coroner Veronica Hamilton-Deeley at Woodvale Crematorium.
The inquest heard Arthur had taken LSD with a friend and he was seen "staggering" on his own before he fell off the cliff.
Members of the public tried to resuscitate him after he was found lying on the ground without any shoes or socks on.
During evidence given by pathologist Dr Simi George, Ms Hamilton-Deeley asked: "The history you had was that LSD was used?"
Dr George replied: "Yes."
The cause of death was given as "multiple traumatic injuries due to a fall from a height".
Recording a conclusion of accidental death, Ms Hamilton-Deeley, said: "I expect the decision and planning to take LSD, or a hallucinogenic drug likely to be LSD, was made on the spur of the moment.
"It's clear he could not know what was real and what was not real.
"It's completely impossible to know what was in Arthur's mind and what he was seeing."
In a statement issued after the inquest, the Cave family said they had been "overwhelmed" by the messages of support from people "in Brighton and beyond".
It read: "Arthur was a wonderfully unruly, creative and free-spirited young man with an infectious, happy, funny daredevil nature.
"He loved his friends and family, idolised his twin brother Earl and was never far from his side."

Like-for-like sales were up by 4.9% during the quarter compared with a year earlier, in part due to the continued success of meal deals.
The company said it would continue to benefit from "low cost pressures and a stronger consumer environment".
But it warned that wage pressures could drive costs up next year.
Chief executive Roger Whiteside told the BBC that the chain already paid staff more than the national minimum wage, but that rising labour costs would lead to "longer term inflationary pressure".
He said the business would "look for cost efficiencies to offset" any rising costs, but added that labour costs "held no fear for us".
Shares in Greggs opened sharply higher and continued to climb in afternoon trading.
"The good times continue to roll for Greggs, with the bakery chain posting an impressive third quarter performance, following on from a dynamic 51.3% increase in first half pre-tax profits," said George Scott at retail analyst Conlumino.
The chain said meal deals, where customers can buy a drink together with food at a discount, were proving popular, particularly at breakfast time.
Greggs has refitted 158 stores this year, while opening 65 and closing 47. The company now has 1,668 outlets.
"We have the High Street pretty well covered," Mr Whiteside said, so most new openings would be in other areas, such as motorway services and garage forecourts.
Musician Nick Cave's teenage son took LSD before he fell off a cliff in Brighton, an inquest has heard.
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Shares in Greggs have jumped more than 10% after the bakery chain reported stronger than expected sales for the July-to-September period.