It came just months after another soldier, Lance Corporal James Ross, 30, from Leeds, was also found hanged in his room, on December 8, 2012.
Both men were serving with the 2nd Battalion The Rifles and had previously been on active service in Afghanistan.
An inquest sitting at Ballymena courthouse is examining both deaths.
Sharon Mitchell told the inquest it was a "perfect storm" of factors that contributed to her son's death.
She described how he had been in debt up to £6,000, an amount that she said would have seemed "insurmountable" to Darren, pointing out he was just 20.
Following his death, she said the owed back pay from the Army settled those debts.
Mrs Mitchell also told the inquest that Darren had told her about two incidents in Afghanistan which upset him.
In one, he had been due to be the soldier at the front of a patrol but was swapped with a colleague at the last minute. That soldier then suffered severe leg injuries in an attack.
She also detailed that towards the end of 2012, he had become hyper vigilant, confided in her less, was jumpy and struggling to sleep.
He had successfully applied for his "dream job" in the Army as an outdoor activity instructor, but this had involved undertaking courses across the UK and in Spain and Germany which left him very tired.
In addition, Mrs Mitchell described how her son had felt isolated after a knee injury held him back from joining his unit in Afghanistan, and instead had to serve with a different unit.