"Much of the day-to-day responsibility for managing the mental health of employees falls on line managers, including implementing stress management initiatives and encouraging those with problems at work or home to seek appropriate help and support. Training in this area is vital to ensure that managers have the confidence and competence to implement policies sensitively and fairly, and can hold difficult conversations with individuals when needed. Training line managers to have an open and supportive dialogue with staff, and having the knowledge to signpost people to specialist sources of mental health support if necessary, are fundamental elements of how an employer should address the psychological aspects of supporting people’s health and well-being at work. "

https://www.cipd.co.uk/binaries/employee-outlook_2016-focus-on-mental-health-in-the-workplace.pdf

This is part of the conclusion from CIPD's July 2016 survey report.  The report contains much interesting data but this conclusion is perhaps the most important.  It does not mean making managers into mental health experts.  It is about helping support and equip managers in their vital people roles, enabling and empowering them to understand and engage with their people when problems may be developing.  It is important also to focus on creating engaging and fulfilling roles and workplaces which provide all employees with connection and purpose, with regular relational one to one conversations which will help employees stay well in our ever more demanding working lives.  A mental health strategy needs to work to reduce the risk of problems developing, as well as deal with what happens when they do.