Stan Kutcher, a noted expert in child mental health, has been named one of Canada's newest senators.

The psychiatry professor is the Sun Life Financial Chair in Adolescent Mental Health at Dalhousie University in Halifax. He was one of four new senators announced Wednesday by Prime Minister Justin Trudeau.

Kutcher told CBC News he received a telephone call about the appointment last week from Trudeau while he was working in Belize developing a mental health program with the Pan-American Health Organization.

He called the appointment "a wonderful opportunity and a challenge."

Kutcher has extensive international experience, having worked in Sub-Saharan Africa, China and South America. Kutcher also ran as a candidate for the federal Liberal party in Halifax in the 2011 election.

He joins new senators from Yukon, Ontario and the Northwest Territories as the latest additions to the Red Chamber.

These latest appointments bring the number of senators to the maximum of 105. It's the first time in eight years the senate has had a full complement of members.