Prevention is better than cure. Be aware of the things that trigger depression and self-destructive behaviours, such as working too hard, placing unrealistic expectations on themselves, being overly self-critical. Learn the warning signs: changes in mood, drinking more, being snappy, poor sleep patterns, not looking after their appearance etc – you’re looking for sustained changes, everyone can have an off day. Get in early and challenge the person about their behaviour. Be firm but not confrontational – argument is counter-productive. Try to help your partner admit there’s a problem, only then can recovery begin. The PHQ9 questionnaire (available online) is a good first tool to see if someone might be depressed and help you get appropriate treatment.

Be a good listener. This is harder than you may imagine, especially if your partner starts talking about things that concern you and you want to answer back. But encourage your partner to open up – it may take time. Be prepared to face uncomfortable issues. To what extent are you part of the problem? Helping your partner may involve making difficult decisions so it is important to show them that you are open-minded and prepared to consider every possibility – but don’t go along with life-changing decisions they want to make while they are still feeling low. They may see things differently as they recover. Don’t tell them they have everything going for them and you don’t understand why they feel so low – it’s not reassuring. But gently helping people see the positives in their own life may be beneficial. Don’t say: “Pull yourself together!”

Be considerate. Do some of the little things that show your partner you care for them and nurture them. Small treats can go a long way. Make time to be together and indulge them. Recognise that your partner is unwell and may not be able to do many of the things they would normally achieve without effort. Be physically and emotionally supportive but don’t collude. Set boundaries for your own mental health. Try to encourage them to set small goals that are achievable, not attempt the impossible.

Encourage exercise and doing things. It can become very easy for a depressed person to stop going out and slowly stop doing things but this rarely helps. Going for a walk with your partner can be very therapeutic and a good opportunity to talk, but don’t push it if they are not ready – just have the walk. Some people find it easier to talk if they are doing something side by side with another person instead of face to face. One of the key aspects to help with depression is doing things and keeping mentally and physically active. Try to encourage them to do small things at first – but little things that bring pleasure.

Don’t let them stop working long term: one of the most important things is structure, and working is a good structure. If they are struggling, a few days off work can be beneficial, but long term it’s rarely a good idea unless recommended by a doctor.

Make sure they are seeking appropriate professional help: via a GP or a counsellor. Depression comes in all forms from mild unhappiness to biological illness and all things in between. Be with them through the process (to the extent that they want this). Make sure that they are not understating their symptoms and failing to get the required support. Antidepressants can have their place and shouldn’t be discounted. Talk to your doctor. Both depression and the tablets you take for it can cause loss of libido – if this is a problem, talk about it and reassure your partner.

Look after yourself. This is important. Living with a severely depressed partner can create feelings of guilt, anger and frustration, which have to be suppressed for the sake of their recovery. However, it’s important to confront any negative emotions and work through them with your partner when they are recovered. Don’t ignore your own health – carers can get depressed too. Make sure you spend time on your own/doing things that make you feel good and don’t be afraid to seek counselling yourself. Also beware self-medication: alcohol and cannabis can make a person feel worse and mask underlying problems.

• The Royal College of Psychiatrists produces a useful leaflet on depression.

The Samaritans, samaritans.org.uk, tel: 116 123, email jo@samaritans.org

Dr Linda Gask, Royal College of Psychiatrists and emerita professor of primary care psychiatry, University of Manchester