Medical literature clearly demonstrates that solitary confinement, the practice of keeping an individual locked up alone in a cell or a room in separation from others, has some very serious effects on health and well-being, and people's ability to be productive citizens and good neighbours on their release.
We need the company of others to maintain a healthy body and mind and our very sense of self.
And yet, a large number of individuals are routinely held in separation from others across New Zealand's prisons and health and disability facilities, sometimes for long periods of time.
My report, Thinking outside the box? A review of seclusion and restraint practices in New Zealand, released today by the New Zealand Human Rights Commission, should make sobering read.
Last year, there were 16,370 recorded instances of segregation in prisons alone. As many as 62 per cent of those segregated were Maori or Pacific Islanders.
In health and disability settings, across all inpatient services, 1000 people were secluded during 2015, some of whom were secluded more than once.
Extreme forms of mechanical restraint, in particular restraint beds and restraint chairs, were still in use in a number of prisons and police custody suites.
In my view, these forms of restraint are inherently degrading and their continued use could violate international prohibitions.
I found that solitary confinement and restraints were not always used as emergency last resort tools and not only for a short time, as required by international law.
I also found material conditions and daily regimes did not always meet international standards, with too many people spending long stretches of time locked up alone in a small cell or room with little to do and with no obvious end time.
They included children, young people and people who were mentally unwell, in breach of international prohibition on such placements.
There are obvious attractions to placing people, some of whom are in highly distressed states, and some of whom are undoubtedly very challenging individuals, apart from others.
That temptation is even stronger for overstretched agencies, where staff and bed shortages mean that it is not always possible for staff to spend the time necessary to manage these individuals in a more appropriate way. Securing a problem out of sight and out of mind.
However, convenience and tight budgets are not good enough reasons to expose vulnerable people to the known dangers of solitary confinement.
There is no justification for keeping a prisoner tied to a restraint bed every night over 36 consecutive nights, or for holding a man with several disabilities in conditions of semi-isolation for years on end.
Vulnerable children in Care and Protection residences, many of whom will have suffered serious trauma already, should not be banished to a barren, locked room resembling a prison cell with nothing to do because they "misbehaved" or, worse still, because they self-harmed.
These are all, nonetheless, examples of practices highlighted by my report.
New Zealand, of course, is not alone. Solitary confinement practices are widespread across the world.
But the current international trend is one of a reduction in the use of solitary and other forms of restraint - a move strongly supported by international human rights and professional bodies, such as the World Health Organisation.
New Zealand can and should be part of that international movement.
Successful efforts to reduce the use of solitary confinement in other jurisdictions, including in the United States and, more recently, Canada, show that where there is a will, there is a way. The same goes for the use of extreme forms of restraint.
New Zealand, and rightly so, prides itself on its human rights record and the initial responses from detaining agencies to my report and its recommendations are encouraging.
I feel cautiously optimistic about the prospects of a meaningful change in current seclusion and restraint policies and practices.
Such change that is required to bring New Zealand in line with international best practice. However, there is no room for complacency.
It will take commitment, determination and hard work to ensure that solitary confinement and forms of restraint are genuinely reserved for a handful of exceptional cases where all else has failed, and then used only for a short time.
But it is an important goal - in line not only with the requirements of international human rights law, but also with principles of good governance and good practice, and pure common sense.
• Dr Sharon Shalev is an Associate at the Centre for Criminology at the University of Oxford, UK. Thinking Outside the Box? A Review of Seclusion and Restraint Practices in New Zealand is available on request from the New Zealand Human Rights Commission or at: www.solitaryconfinement.org/New Zealand.