More than one in eight registered patients in St Helens have been diagnosed with depression, one of the highest rates in England.
New Public Health England data shows that, between April 2017 and March 2018, the proportion of patients in the local authority with depression was 13.4%.
And this figure has risen from 8.2% in 2013-14.
At the same time, in St Helens, the percentage of patients being diagnosed with the mental health condition for the first time has increased from 1% to 2%.
Charities say the rise in prevalence could be due to less stigma surrounding depression.
Stephen Buckley, head of information at mental health charity Mind, said this could be positive “if more people feel they can ask for help”.
“It might also be that GPs have a greater understanding of mental health and are more able to spot symptoms of depression,” he continued.
“However, it’s crucial that resources are made available to GPs to cope with this increase in demand.”
Mr Buckley said it was essential GPs have the correct training, as most people go to their local doctor for support for their mental health.
“As part of the NHS long term plan, due very soon, we need to see a plan for how Government will work together to make sure people with mental health problems can get the right support,” he added.
St Helens has a higher proportion of patients with depression than the North West does overall, where 11.7% of patients on GP lists are diagnosed with the condition.
There are large regional variations across England. Rochdale has the highest prevalence, where more than one in seven patients have been diagnosed with depression, while in Newham, east London, more than one in 20 have the condition.
Lucy Schonegevel, from the charity Rethink Mental Illness, said a huge amount of work has been done over the past decade to “reduce the stigma associated with mental illness”.
She explained: “People are more likely to now reach out for help and rightly not feel ashamed to do so.
“We also have better data collection now than in previous years, so we have a more accurate picture of mental health problems across the nation.”
Ms Schonegevel added that a rise in demand must be matched by “much needed improvements to services”.
A Department for Health and Social Care spokeswoman said: "Mental health is a key priority for Government. We are transforming services with record amounts of funding, with the NHS spending almost £12 billion on mental health last year.
“We have introduced access and waiting time standards, expanded talking therapies, and are revitalising crisis care services."