McDonald, who has recently been appointed non-executive director at Mental Health First Aid England, told HR magazine a historic failure of the two departments to work together meant "very little progress" was made around workplace mental health.
"A strategic alliance between the two departments has been important in bringing about positive change," he said. "A large part of the solution is being more proactive in your approach to mental health issues. You have to look at how you can prevent people getting ill in the first place."
Failures around mental health begin long before people even reach working age, according to McDonald.
"In schools and universities there is no education around the need to keep your mind healthy," he said. "While most people have physical education, there is no class that teaches the equivalent in mental health.
"With increasing uncertainty and volatility leading to greater pressures in the world today, it's vital we address this."
McDonald also believes that employers should be offering the same support for mental wellbeing as they do for the physical fitness of their staff.
"There are often gyms in workplaces now, so why not have spaces where people can practice mindfulness and reflection for an hour or so?
"My friend lost his life two years ago because of mental health issues. I suffered myself with anxiety and depression also. The reason I'm here and he's not is that I had support for my illness," he added.
Employees not speaking out about mental health
Four in 10 employees have suffered from stress, anxiety or depression and not told their employer, according to research by insurance and pensions provider Friends Life and Business in the Community.
The survey of 2,000 British adults also suggests one-half of employees are reluctant to talk about mental health problems because they feel it may damage their career prospects.
Friends Life corporate responsibility manager Roger Cotton told HR magazine people are still concerned colleagues will associate mental health issues with "incompetence and weakness".
"We need to educate managers to have these conversations with their staff," he said. "Having a champion for mental health issues in the boardroom is also a great help. Someone needs to provide leadership in this area."
He added that spotting the signs of mental health problems is a big part of the battle.
"Sometimes we even deny there is something wrong to ourselves," he explained. "So we need to get better at seeing the symptoms in other people. People's behaviour will change. They may become irritable or physically run-down. Colleagues can offer support if they know what they're looking for."