Last Night's TV: Cutting Edge: My New Brain/Channel 4<br />The Wounded Platoon/BBC2

Taken out of context it would have sounded like classic parental exasperation. "His concentration is poor, his ability to plan things and get himself organised is hopeless... just out to lunch." But Simon, the object of this description, isn't a teenager any more and – despite the informality of the last few words – this was a clinical assessment not a moan, a neurologist's evaluation of damage done. Simon, who walked like an old man and found it difficult to hold a one-item shopping list in his mind, wasn't a typical instance of youthful fecklessness but a specific example of brain trauma. After a lively evening at Newcastle University ("We weren't exactly completely sober or teetotal," said a friend), he'd tried to sneak back into a nightclub he'd just been ejected from and had fallen 20ft on to concrete. Cutting Edge's film My New Brain followed his progress as he tried to come to terms with the aftermath of his accident.

It was an upward slope, but a painfully gentle one. After five weeks in a coma, Simon had woken to a radically different life, one in which his ability to perform even the simplest of tasks had been compromised. When his mother came to visit him in the rehabilitation unit where he was receiving therapy, he treated her arrival as if it was a delightful novelty, rather than the daily routine it actually was. He had to talk himself through having a shower, with a nurse hovering nearby, just in case he forgot which bits he'd washed and which he hadn't. And, more cruelly, as he healed he became more aware of just how damaged he was. His anger emerged in some commonplace ways – rage and swearing at his mother – and in some odd ones. He developed a fixed hatred of the family dog, his conversation repeatedly looping round to how he was going to kill it: "I want to batter someone around the head... and he's not a nice dog," he said, accompanying the threat with a chuckle that was like a ghost of his previous self.

He also obsessed about his accident – his thoughts always prone to drop into a rut that would take him back to the moment at which his old self and his old life were destroyed. "Pointless mistake, drunken mistake," he muttered angrily, expressing the view that he was singularly unlucky. He does have good fortune in one respect, though – a family which is riding out the disappearance of the person they loved and the arrival of a more difficult substitute with patience and tenderness. On the morning of his 21st birthday – a bittersweet occasion which concluded Cutting Edge's film – he'd punched his younger brother in the face. By the evening it had all been forgotten... and his brother's warm affection and Simon's dazed awareness of the distance he still had to travel made you want to weep.

Sudden impact isn't the only way of damaging a human brain, as was made abundantly clear in The Wounded Platoon, a film about an American army unit which had a distinguished record in Iraq and a notoriously undistinguished one back home. Altogether, 17 soldiers from Fort Carson in Colorado Springs have been charged with murder, attempted murder or manslaughter since returning home from active duty – and Dan Edge's film concentrated on three of them, all of whom served together. They were part of 3rd Platoon, Charlie Company, a unit which suffered more casualties than any other in their company and was part of a battalion that had a casualty rate eight times higher than other similar groups. Their mission – which they nicknamed "Mad Max" – was effectively to get shot at, patrolling a particularly dangerous highway to draw insurgents out into firefights. They had also been badly affected by the death of a much-admired sergeant after an attack by a suicide bomber.

These were not men you'd want to cross, either in Iraq, where helmet-camera footage recorded their brittle, furious contempt for local civilians, or in Colorado, where they found the adjustment to civilian life very difficult. The point of Edge's film was not to indict individuals for their brutality, though, but to point a finger at the American military, which overlooked its own guidelines on recruitment to fill the gaps in the front line. Men showing clear signs of post-traumatic stress disorder were patched up with pharmaceuticals and sent out into intense combat – and they had been given virtually no assistance with the psychological wounds they'd sustained when they came back. They were, in a way, improvised explosive devices – and there was no great shock in the fact that they eventually went off, particularly given the cocktail of drugs they'd been given. Nor were they unrepresentative: in the last 10 years, more US troops have committed suicide than have been killed in combat in Afghanistan.

"If you're not numb in those moments you're going to go crazy," said one soldier, recalling the horrors of collecting murdered Iraqis off the streets and seeing his friends blown to pieces. The Catch-22 was that going numb in those moments is a kind of craziness, a severance from normal reaction which can easily turn lethal. He was currently serving 52 years for attempted murder in Colorado – and nothing at all (at least officially) for the casual killings of civilians that he claimed were routine in Iraq. He'd been turned into a weapon – and they'd realised too late that the aim was indiscriminate and there was no trigger guard.

t.sutcliffe@independent.co.uk