Around 83.4 percent of Syrians live below the poverty line compared with 28 percent in 2010, the report by the UN Economic and Social Commission for Western Asia (ESCWA) and the University of St Andrews said.
An estimated 13.5 million people in Syria needed humanitarian aid by late 2015, and more than 4 million of these were in Damascus and Aleppo provinces.
"According to one estimate, life expectancy dropped from 70 in 2010 to 55.4 in 2014," the report said.
Around half of Syria's 493 hospitals in 2010 have been seriously damaged in the war, it added.
"The deliberate targeting of doctors and pharmacists has forced many to flee the country, at a higher rate than that of the average population.
"As a result, the number of persons per doctor in the country rose from 661 in 2010 to 1,442 in 2015."
Around 12.1 million Syrians lack adequate access to water, sanitation and waste disposal, the report said.
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Destruction of housing and infrastructure was estimated at around $90 billion.
Damaged pumps and pipelines led to the loss of almost half of potential drinking water supply in 2015, the Syrian General Establishment for Drinking Water and Waste Disposal was cited as saying.
Drinking water per capita dropped from 72 cubic metres to 48 cubic metres between 2011 and 2015.
The numbers were just as bleak in education, with around 2.7 million children of school-age out of school both inside and outside Syria, the report said.
The economy contracted by 55 percent between 2010 and 2015, when it had been expected to grow by 32 percent.
Gross domestic product in farming fell by nearly 60 percent between 2010 and 2015, notably because of fighting and the high cost of irrigation, leading to a sharp increase in the cost of food.
The price of wheat flour and rice rose by 43 percent and 89 percent respectively between 2014 and 2015.
Syria's war has killed more than 270,000 people and displaced millions since it erupted after the brutal repression of anti-government protests in 2011.