Great Depression was caused directly by the failiure of government and Federal Reserve's wrong monetary policies. Even the chairman of Federal Reserve (which was the government instutiton responsible for the monetary policy of the US) Ben Bernanke acknowledged that fact. US Government, by intervening the economy, turned a recession into a crisis. American economy between 1930 and 1940 failed to add anything to its capital stock: net private invesment for that eleven year totaled minus 3.1 billion dollars. Without capital accumilation, no economy can grow. If demagoguery were a powerful means of creating prosperity, then FDR might have lifted the country out of depression in short order. But in 1939, ten years after its onset and six years after the commencement of the New Deal, 17.2 percent of the US labor force, officialy, remained unemployed. So in short New Deal didn't heal anything it only worsened and prolonged the situation.
