Mr Corbyn appointed Liverpool Wavertree MP Ms Berger as the first dedicated shadow minister for mental health in the reshuffle following his leadership victory on Saturday.
The GPC said the appointment could encourage the government to take mental health 'more seriously', but stressed it was important for the 'rhetoric to match reality'.
In her previous role as Labour’s shadow public health minister, Ms Berger frequently spoke out for greater emphasis on mental health.
The 34-year-old will work closely alongside Heidi Alexander, the newly appointed shadow health secretary who takes over the role from Andy Burnham.
Mental health prioritised
Both Ms Berger and Ms Alexander backed Mr Burnham in the race to become Labour leader. He has been appointed shadow home secretary after coming second to Mr Corbyn.
GPC deputy chairman Dr Richard Vautrey said: ‘It’s certainly good that mental health is being prioritised.
‘But while having a named person in a certain role is quite important, the key thing is what they can actually deliver. We need to see the promise of parity of esteem for mental health turn into reality, and that’s difficult for an opposition party to do.
‘It’s up to the government itself to make change happen, but I'm sure having a focus on mental health from the opposition’s perspective will encourage both the NHS and government to take the issues related to mental health that bit more seriously.’
Shadow cabinet reshuffle
In a statement on the shadow cabinet reshuffle, Mr Corbyn said: ‘I am delighted that we have established a shadow cabinet position for mental health which is a matter I have long been interested in.
Dr Vautrey added that it was promising to see leading politicians increasingly recognising the importance of mental healthcare.
‘We have seen individuals carrying a significant mental health brief,’ he said. ‘We saw that in the last coalition government – Norman Lamb had a particular interest in mental health and was pursuing that agenda quite vigorously.’