As the researchers report in Psychological Science, those with high self-esteem who repeated “I’m a lovable person” scored an average of 31 on mood assessment compared with an average of 25 by those who did not repeat the phrase. Among participants with low self-esteem, those making the statement scored a dismal average of 10 while those that did not, managed 17.

Dr Wood suggests that positive self-statements cause negative moods in people with low self-esteem because they conflict with their view of themselves. When positive self-statements strongly conflict with self-perception, there is not mere resistance but a reinforcing of self-perception. People who view themselves as unlovable, find saying that they are so unbelievable that it strengthens their own negative view rather than reversing it. Given that many readers of self-help books that encourage positive self-statements are likely to suffer from low self-esteem, they may be worse than useless.