I’m a psychiatrist. When people discover this, after the obligatory, “Are you analysing me right now?” (no – at least not in the way you think), the next question is nearly always, “Do you section people?”

For the uninitiated, being “sectioned” in England and Wales means being detained in a hospital under the Mental Health Act (MHA). This can happen if someone is experiencing a mental disorder of a “nature and degree” that could jeopardise their health or safety or the safety of others, and they are unwilling or unable to agree to hospital admission.

To put it bluntly, detaining somebody under the MHA is a big deal. Normally you can’t deprive someone of their liberty unless they’ve committed a crime. That isn’t the case, however, if three senior mental health professionals agree that detention is the right course of action. There are checks and balances within the MHA, but the truth remains: a fundamental human right can be bypassed for the purposes of managing a mental disorder.

I am an NHS consultant liaison psychiatrist, meaning my area of expertise is the interface between physical health and mental health. Often I work in the accident and emergency department, providing the kind of support the chancellor promised to bolster as part of last month’s budget, which contained plans for a much-needed increase in funding for mental health crisis services. Whatever the financial context though, assessing patients for detention under the MHA is always part of my role. It might be a young man with schizophrenia who has been brought to A&E by his desperately worried family as he has become consumed by voices telling him to kill himself; a woman with a depression so severe that she has lost the ability to eat or drink and requires feeding with a tube; or an elderly man originally admitted due to a fracture, but whose recovery has been railroaded by the fact that his dementia has caused him to become incredibly agitated on the ward.

I think of the MHA as a life-saving intervention. Just as an A&E doctor will use a defibrillator to shock a patient’s heart back into life, I will advise detaining a patient under the MHA with the intention of saving life too. Most commonly, the life at risk is the patient’s own. But the MHA asks us to consider the “protection of other people” too, which puts psychiatrists in the difficult position of balancing the needs of the individual patient against the needs of the community. (At this point let me emphasise that people with a serious mental illness are much more likely to be the victim, rather than the perpetrator of a crime, although you would be forgiven for thinking otherwise based on how this issue is portrayed in some media.)

Psychiatrists are sometimes characterised as power-hungry creatures who get their kicks from being able to exert control over others via the MHA. Although it would be wrong to pretend a power differential doesn’t exist, I can wholeheartedly say that if I never had to section a person ever again I’d be thrilled. That’s because this would mean that every patient I saw would be willing and able to receive the necessary care for their mental health problems in a truly collaborative manner – that would be therapeutic gold. Sadly, just as I can’t envisage my A&E colleagues packing away the defibrillator any time soon, I think that the MHA will need to remain a vital tool in helping people with serious mental health problems for the foreseeable future.

This is not to say that it is without problems. Far from it. We have to grapple with some highly uncomfortable truths, for example that a hugely disproportionate number of black and minority ethnic people are detained. We don’t fully understand why this happens and it is one of the reasons that an independent review of the MHA is currently under way.

You don’t have to be an expert in empathy to appreciate that being sectioned is probably one of the most stressful things that could happen to someone. It affects not only them, but their friends and family too. As somebody who likes to be in control of my own destiny, the thought of a group of professionals deciding that they know better than me about what is needed for my mental health is a concept that fills me with horror.

It is always a challenging experience to section somebody. It might be straightfoward clinically and legally, but it is never easy. I’m not impervious to the distress of patients and their loved ones. For patients who are unwilling (rather than unable) to agree to treatment, I try to get them to a point where, although they might vehemently disagree with me, they can understand why I’m advising that detention is necessary.

Perhaps unexpectedly, the cases that I’ve worried about the most are ones where I’ve decided not to detain a patient. Although three suitably qualified professionals must agree in order to detain someone, the process itself is generally initiated by just one senior doctor, like me. If I decide not to section somebody, then they won’t be detained at that point in time.

Many psychiatrists’ careers have been marked by troubling cases of the following kind: we have been deeply concerned about an individual and wanted to admit them to hospital, but after listening to their strong desire to have treatment at home and carefully negotiating a community treatment plan with colleagues and their family, we have decided not to section them. Sadly, within a few days, we hear these patients have died due to suicide. This is devastating for all concerned.

Psychiatrists cannot predict the future. We aim to make the best decisions that we can by assessing the needs and desires of our patients through the lens of our professional expertise. It is impossible to know whether if different decisions had been made for these patients, they would still be alive today. Such cases will forever haunt me; coping with this degree of uncertainty is undoubtedly one of the hardest aspects of my work.

So, yes, I can section people. But never with the zeal that the questioner suggests. Always with the enormous sense of responsibility that can only be generated by decisions relating to life and death.

• In the UK, Samaritans can be contacted on 116 123 or by email on jo@samaritans.org. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14. Other international suicide helplines can be found at www.befrienders.org.

• Mariam Alexander is an NHS consultant liaison psychiatrist