Michael Douglas fully supports Catherine Zeta-Jones' decision to seek treatment for her bipolar II disorder again.

The 68-year-old 'Behind the Candelabra' star is 100% devoted to his Welsh actress wife of twelve years, who is expected to complete a 30-day program as a ''proactive'' measure to help with her condition, which can cause high and low mood swings as well as depression.

A friend close to the couple told People.com: ''He couldn't be more supportive, just like she is of him. They're solid.

''They're really, really devoted to each other.''

The couple, who have been subject of divorce rumours several times this year, were last seen together in New York last Monday (22.04.13) at the Film Society of Lincoln Centre's 40th Annual Chaplin Award Gala, honouring Barbra Streisand.

An eyewitness said: ''Catherine was on his [Michael's] arm much of the time. She seemed really relaxed and happy. I saw her with a cocktail and she was socialising and enjoying the evening ... Nothing seemed out of the ordinary, and they both seemed to be having a good time.''

The 43-year-old 'Chicago' star, who has two children, Carys, 10, and Dylan, 12, with Michael, first sought medical help in 2011 when she spent time in a Connecticut-based mental health facility and her spokesperson Cece Yorke confirmed she re-entered treatment in recent days.

She previously said: ''Catherine has proactively checked into a health care facility.

''Previously Catherine has said that she is committed to periodic care in order to manage her health in an optimum manner.''

A friend of the star's added that she simply wants doctors to monitor her medication this time, saying: ''There was no big problem. This was just a good time to do it. She is in between projects.

''This has always been part of the plan. She would manage her health. She is vigilant about it.''