People in the states of former East Germany are the unhappiest in the country, according to the 2014 Glückatlas (Happiness Map) for Deutsche Post.
Schleswig-Holstein, Hamburg and Lower Saxony topped the table.
Bavaria and the south ranked in the middle, while Berlin was near the bottom due to low scores for work, income and health.
The map divides Germany up into 19 regions rather than to its 16 states.
The general happiness of the Germans has slowly increased from 6.6 in 2004 and is now put at seven on the zero to ten index, which was presented in Berlin on Wednesday.
But the gap in happiness between East and West Germany is growing. In 2014 it stood at 0.36 points, up from 0.2 points in 2012. In 1991 after reunification it was 1.3 points.
The study put the difference down to the gap in wages and economic performance between eastern and western states.
“Germany is a happy country,” leader of the study Professor Bernd Raffelhüschen said, adding Germans had been on a “happiness plateau” for years.
Germans' average happiness level of seven places them ninth in Europe, behind leaders Norway (8.8), Sweden (8.2) and the Netherlands (7.9).
There have been improvements in Germans level of satisfaction regarding their income, work and family life, but less progress with their happiness when it comes to health, leisure time and living situation.
The happiness index is compiled from data from the German Social and Economic Panel (SEOP) survey of 30,000 people comprising almost 11,000 households.
Meanwhile, a separate survey of expats in Germany, found that almost half (47 percent) of expats in the country were satisfied with life.
Germany ranked well for quality of life, work and family life, but scored very poorly for ease of settling in.
Just 13 percent of expats surveyed said Germans were very friendly towards foreigners.
SEE ALSO: How to understand the north Germans