A former soldier who turned to trafficking drugs was released from prison early after it was revealed he was suffering post-traumatic stress disorder.

A former Australian soldier who became a drug courier has been granted an early release from prison because he had post-traumatic stress disorder.

Jason Damien Gaerlan, 30, was serving a six-year prison sentence for drug trafficking after police found methamphetamine valued at almost $395,000 in his car in 2010.

His car was stopped on the Bruce Highway near Bundaberg, in central Queensland, as he tried to drive the drugs from Sydney to Townsville.

The sentencing judge took into account how Gaerlan had served in the Australian Army from 2002 to 2008 and toured Iraq and East Timor.

The former soldier was to become eligible for parole in November, after two years in jail, but in May he appealed against his punishment from prison after seeing a psychologist.

Dr Robert Zemaitis’s statement presented to a Supreme Court hearing in Townsville last month said his patient was and had been suffering from chronic post-traumatic stress disorder after exposure to “extremely traumatic experiences” overseas.

Dr Zamaitis said it was not unusual for former soldiers to use alcohol or drugs to cope with civilian life, and his decision to courier drugs came after a “deterioration in his cognitive functions”.

Gaerlan’s statement said he had resisted seeking treatment as a soldier and only sought psychiatric help in prison after having negative thoughts.

After hearing the new evidence, the Court of Appeal in June reduced Gaerlan’s overall sentence to five years and suspended it immediately, after he had served about 20 months.

Justice Robert Gotterson said in a written judgement published on Tuesday that the new evidence was significantly relevant.

“By revealing the link between the applicant’s psychological state and the offending, the evidence has an impact on the criminality of the latter,” he wrote.

Gaerlan was placed on probation for three years.