Chapter 1. Introduction

The occurrence of atopic disorders has been increasing in Western countries in recent years (Konsensuslausuma 1998, Pekkanen et al. 2001a, Savolainen 2001, Hannuksela 2002). In Finland, about one million people (about 20% of the total population) are estimated to having some manifestation(s) of atopic disorders, e.g., asthma, allergic rhinitis/conjunctivitis, or atopic dermatitis (Savolainen 2001). Correspondingly, data from the Health 2000 study showed that 5% of adult Finns have suffered from major depression during the past 12 months (Pirkola et al. 2002). Major depression is one of the most important of all the illnesses leading to functional disability worldwide (Murray & Lopez 1997, Isometsä et al. 2000), and despite the increasing use of antidepressant medication, an upward trend in depression-related working disability has also been reported in Finland (Salminen et al. 1997, Herva 2002). Thus, both depression and atopic disorders are illnesses of major public health concern in Western countries (Konsensuslausuma 1998, Galil 2000, Isometsä et al. 2000).

Several lines of evidence suggest that there exists a link between atopic disorders and depression (Bell et al. 1991, Wamboldt et al. 1996, 1998, 2000, Hashiro & Okumura 1997, 1998, Cohen et al. 1998, Cuffel et al. 1999, Hurwitz & Morgenstern 1999, Brown et al. 2000, Centanni et al. 2000, Goethe et al. 2001). The majority of these atopy-depression studies are, however, based on clinical data settings including patients suffering from either depressive or atopic conditions, and the studies are furthermore heterogeneous in case definitions. There is a need for population-based investigations, which confirm the atopy-depression association at epidemiological level by using appropriate and accurate tools to define the presence of atopic disorders and depression.

Professor (emerita) Paula Rantakallio started the prospective Northern Finland 1966 Birth Cohort in order to describe and analyse the risk factors leading to perinatal deaths and low birth weight (Rantakallio 1969, 1988). The present study belongs to the psychiatric part of this ongoing follow-up project, called nowadays the Northern Finland Health and Well-being Study. This genetically homogeneous database made it possible to investigate the putative atopy-depression association at general population level. The presence of atopic disorders could be verified by objective measurements, i.e., skin prick test responses, and depression by different indicators, e.g., carefully validated hospital-treated depression diagnoses (Isohanni et al. 1997, Moilanen et al. 2003).