The number of times people in Scotland have been detained for mental health treatment has risen by 10.5% in the last year.
The Mental Welfare Commission said the figure is more than double the average 4.5% rise over the previous five years.
The report also showed safeguarding measures for people being detained against their will are at their lowest in 10 years.
Consent of a mental health officer (a specialist social worker) is an important safeguard and should happen every time a person is detained using the Mental Health Act, the commission said.
But consent fell below half for emergency detentions last year.
Julie Paterson, chief executive of the Mental Welfare Commission, said she is “very concerned” over the way detentions are taking place.
She said: “We don’t know why this is, but we are concerned.
“Every detention is the deprivation of a person’s liberty, albeit for the best possible reason in wishing to treat that individual.
“The question is whether more people in the population are becoming more seriously unwell every year, with last year’s spike even more pronounced.
“Or whether services are under such pressure that people wait too long, and only receive care and treatment once they have become so unwell they require to be detained.
“Whichever is the case, these rising numbers suggest that pressures on mental health services increased significantly last year.”
For the first time NHSS also compared levels of detention with deprivation, and found a link between detention for serious mental ill health and poverty.
According to the Scottish Index of Multiple Deprivation (SIMD), people from the 20% most deprived areas in the country accounted for 38.3% of emergency detentions, 32.2% of short-term detentions, and 29.6% of compulsory treatment orders.
The report also shows higher numbers of detentions for people from ethnic minority groups compared with general population levels.
About 4% of Scotland’s population identifies as from an ethnic minority (Asian, African, Caribbean or black, other or mixed), according to the NHSS.
The data revealed the proportion of people detained for mental health treatment from these groups were 6% for emergency detentions, 7.4% for short-term detentions, and 7.6% for compulsory treatment orders.
Ms Paterson added: “This report is not the first to show a link between deprivation and mental ill health, but for the first time we see these inequalities among people detained for mental health care and treatment.
“We hope that by sharing this information, and our data on ethnicity, geographical variations and other aspects of detention, we can support government and services to ensure they provide the right levels of resource and support for vulnerable communities at the right time.
“We also call once again for urgent action to ensure mental health officer consent to emergency detentions, wherever practicable.”
The new figures confirm there were 6,699 episodes – each being a single period of time one individual is detained – using the Mental Health Act in Scotland in 2020-21.
There are different ways people can be detained – either by emergency certificate, short-term detention, or through a compulsory treatment order – and rates rose in each.