Daniel Hadley, a former police officer and the son of broadcaster Ray Hadley, has had a charge of cocaine possession against him dropped in a Sydney court.

Hadley, 28, was arrested in August after he was found with 0.79 of a gram of the drug at a Rouse Hill pub.

A former senior constable with NSW Police, Hadley resigned from the force a month later.

At Parramatta Local Court today, magistrate Garry Still dismissed the charge under the Mental Health Act, discharging Hadley into the "care of a responsible person".

Daniel Hadley (left) has had a cocaine charged against him dismissed on mental illness grounds. (9News)

Ray Hadley outside court today. (9News)

Ray Hadley was in court to support his son.

"It's been a very tough time, from the first media conference we gave when this all occurred," the radio host said.

"It's been a rollercoaster."

Daniel Hadley resigned from the NSW Police Force after his arrest. (Supplied)

Hadley said his son had been suffering from post-traumatic stress disorder, stemming from his time as a police officer.

"Daniel was very good at hiding," Hadley said.

"We had no idea he was battling with these issues and had been battling, according to his GP, for quite some time.

"I'm not here with sage advice for parents and grandparents to say 'keep an eye on your sons and daughters, your husbands and wives or the coppers'.