Depression is not an allergic reaction (Is depression a kind of allergic reaction?, 5 January). Allergic reactions are appropriate immune responses against foreign materials. An autoimmune process may underlie some cases of depression, though we do not know how much of a role inflammation plays. Anti-inflammatory drugs have so far not yielded promising results in preliminary trials. The role of autoimmune inflammation in stand-alone depression is far from conclusive (Anti-inflammatory drugs ‘could fight depression’, 20 December). We know that depression is associated with impaired serotonergic and noradrenergic neurotransmission which impairs the brain’s ability to form new neural networks. The treatment of depression involves antidepressants that help correct the underlying biochemical abnormality. Adherence to medication regimens from your doctor is therefore important. Psychological and social intervention is also important: helping people make sense of their problems and devise strategies to overcome them. Cognitive behavioural approaches help retrain previously maladaptive ways of thinking. Further research into the neurobiological basis of mental disorders is needed. However effective psychological and social support is also needed.
Dr KD Jethwa Nottingham University Hospitals NHS Trust

Research has now shown that competitiveness and self-focused achievements operate through different brain systems than those for concern for others and altruistic motives. Indeed stimulating one motivational system can tone down the other. Understanding these basic facts about the human brain is essential if we are to move towards a more just and moral society. Basically if you overdrive the competitive system, focusing on high rewards which give a dopamine rush (such as bankers’ bonuses) you risk toning down altruistic motivation systems. Some wealthy people are philanthropists, but many are not and don’t see the problem in taking a massive share of available resources because they’re locked into a competitive, self-focused (brain) system. In the case of politics, too, if people focus on developing arguments to destroy the arguments of others (rather than promote the good) they risk toning down their altruistic motivational systems. Individuals caught up in these basic motives systems can struggle to emotionally connect with the suffering of others. The problem for politicians is that audiences know whether they are presenting their arguments simply to beat their opponents, or actually to create good. Tricky, given the brain that evolution has given us.
Professor Paul Gilbert Mental Health Research Unit, Derbyshire Healthcare NHS Foundation Trust

Three cheers for Hilary Mantel’s dismissal of the simplistic concept of grief as an essentially linear process ( Review, 27 December). Many people’s experience suggests that Kübler-Ross’s “stages” of grief are rather aspects of grief, that may be experienced in different orders and different combinations. Indeed the co-existence of separate, and often conflicting, emotions is a part of what makes grief difficult to describe. For some people, it is like being in a small craft on a large ocean: sometimes there are calm waters and blue skies; on other days great grey clouds exclude all light. And occasionally it seems that terrible whirlpools are going to suck the sufferer down into extinction. Insisting that there is a “grieving process” and that at any one time any given sufferer will be at a certain stage and progressing towards the next is entirely counterproductive.
PB Alldred  Leverburgh, Isle of Harris

This article first appeared in The Guardian, 13 January 2015.